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  • 36.40  (114)
  • Saccharomyces cerevisiae  (90)
  • Springer  (204)
  • American Meteorological Society
  • 1995-1999
  • 1990-1994  (204)
  • 1993  (110)
  • 1991  (94)
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Keywords
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  • 1995-1999
  • 1990-1994  (204)
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  • 1
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    Springer
    Journal of industrial microbiology and biotechnology 7 (1991), S. 131-135 
    ISSN: 1476-5535
    Keywords: Saccharomyces cerevisiae ; Jerusalem artichoke ; High-fructose syrup ; Ethanol ; Immobilized yeast cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The results from this study showed that Jerusalem artichoke juice can be used for the production of very enriched fructose syrup by selective conversion of glucose to ethanol in a continuous process using immobilized cells ofSaccharomyces cerevisiae ATCC 36859. The product contained up to 99% of the total carbohydrates as fructose compared to 76% in the feed. Using Jerusalem artichoke juice supplemented with some glucose a product was obtained with 7.5% w/v ethanol which made ethanol recovery economically favourable. It was found that some fructose was consumed in these continuous processes; the glucose/fructose conversion rate ratio was regulated by the glucose concentration in the product stream.
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  • 2
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    Journal of industrial microbiology and biotechnology 7 (1991), S. 181-189 
    ISSN: 1476-5535
    Keywords: Saccharomyces cerevisiae ; Torulaspora delbrueckii ; Aroma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Thirty-three fermentations of Pedro Ximénez grapes, collected in three degrees of ripeness, were carried out by inoculation with three types of inoculum: pure cultures ofSaccharomyces cerevisiae races and ofTorulaspora delbrueckii, indigenous yeasts, and mixed cultures of indigenous yeasts enriched with the pure cultures. By means of variance analysis 21 compounds were determined whose final concentrations in the wines significantly depended on the musts, the inocula or both. Eleven products that depended significantly on the inocula were subjected to a discriminant analysis in which most of the pure cultures gathered in a discriminant space area different from that occupied by the indigenous yeasts. The centroids corresponding to most of the mixed cultures were shifted to the central area of the discriminant space, moved away from their corresponding pure cultures and approached the indigenous yeasts. The results show a high similarity between the fermentations carried out with mixed cultures with the addedS. cerevisiae races and those fermentations carried out with the indigenous yeasts, with regard to those compounds which were significantly dependent on the inocula.
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  • 3
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    Applied physics 52 (1991), S. 84-89 
    ISSN: 1432-0649
    Keywords: 36.40 ; 42.65 ; 47.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Coherent Stokes and anti-Stokes Raman scattering CSRS and CARS have been employed to study the spectroscopy of nitrogen molecules and clusters in the expansion of a supersonic jet. In the vibrational spectrum, at strong stagnation conditions, an intense redshifted peak is observed which can be assigned to the intramolecular vibrations in large N2 clusters having adopted the β-phase structure. Another weak feature is assigned to nitrogen clusters in the α-phase. In the rotational region of the spectrum only monomer features have been observed. The failing to observe librational motions is consistent with the finding that the nitrogen clusters are predominantly in the orientationally unordered β-phase. The low rotational temperature suggests supercooling of the β-phase.
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  • 4
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    Applied physics 53 (1991), S. 353-361 
    ISSN: 1432-0649
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We are investigating the thermodynamic conditions under which condensation occurs in laser ablated copper plasma plumes. The plasma is created by XeCl excimer laser ablation (308 nm, 300 mJ/pulse) at power densities from 500–1000 MW/cm2 into backing pressures of helium in the range 0–50 torr. We use laser-induced fluorescence (LIF) to probe velocity and relative density of both atomic copper and the copper dimer molecule, Cu2, which is formed during condensation onset. At low pressure (10 mtorr), the atomic Cu velocity peaks at approximately 2×106 cm/s. Copper dimer time-of-flight data suggest that condensation onset occurs after the Cu atoms have slowed very significantly. Excitation scans of the Cu2A-X (0,0) and (1,1) bands yield a rotational and vibrational temperature in the neighborhood of 300 K for all conditions studied. Such low temperatures support the theory that Cu2 is formed under thermally and translationally cold conditions. Direct laser beam absorption is used to determine the number density of atomic copper. Typical densities attained with 5 torr of helium backing gas are 6–8×1013 cm−3. Rayleigh scattering from particulate is easily observable under conditions favorable to particulate production.
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  • 5
    ISSN: 1432-0983
    Keywords: Schizosaccharomyces pombe ; Saccharomyces cerevisiae ; Argininosuccinate lyase ; Sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The complete nucleotide sequence of the ARG7 gene, coding for argininosuccinate lyase (EC 4.3.2.1), in the fission yeast (Schizosaccharomyces pombe) has been determined. It consists of an open reading frame of 461 codons. The deduced protein has a molecular weight of 51 200 Da. The gene is devoid of introns which is confirmed by the fact that it is expressed in Escherichia coli after spontaneous insertion of a bacterial sequence probably bearing a prokaryotic promoter. A perfect “TATA” box is found at-72 and the major transcription initiation site in Saccharomyces cerevisiae is located at-11 as shown by primer extension experiments. Comparison of the S. pombe lyase with related proteins from other organisms reveals an important degree of conservation except in the carboxyterminal part of the polypeptide. Additionally, a deletion removing 66 amino acids of the carboxy terminus yields an enzyme exhibiting some biological activity. A unique 1500 b transcript was found in S. cerevisiae when the intact gene was present, but the deleted version of the gene gave rise to at least three transcripts of 1800, 2800 and 3900 b.
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  • 6
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Pyrimidine salvage pathway ; Semi-dominant mutants ; FUR1 ; Uracil phosphoribosyl transferase ; Regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Saccharomyces cerevisiae, the protein encoded by the FUR1 gene is absolutely required for the expression of uracil phosphoribosyl transferase activity. The occurrence of semi-dominant mutations for 5-fluorouracil-(5FU)-resistance at this locus led us to clone and sequence the semi-dominant fur 1–5 allele. A single point mutation, resulting in the substitution of arginine 134 for serine, is responsible for this mutant phenotype. The fur 1–5 allele is transcribed and expressed at the same level as the wild-type allele. But, in contrast with the wild-type, the UPR Tase activity of the fur 1–5 mutant strain is stimulated in vitro by UTP and does not, therefore, correspond to a loss of feedback of UPR Tase activity. We found that uracil, as a free base, induces a significative increase in transcription and UPR Tase activity in a wild-type strain as well as in uracil-overproducing mutants which principally explains the high efficiency of the pyrimidine salvage pathway in S. cerevisiae.
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  • 7
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Centromere flanking sequences ; tRNA modification enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transcriptional analysis of the region flanking the left boundary of the centromere of chromosome VI revealed the presence of a gene immediately adjacent to CEN6. The transcription of the gene is directed toward the centromere, and nucleotide sequence analysis showed that the coding region terminates only 50 bp away from CEN6. Our results extend to chromosome VI the observation that centromere-flanking regions of S. cerevisiae are transcriptionally active. Disruption of the coding region of the gene showed that its product, whilst not essential for cell viability, is important for normal cell growth. The gene has been termed DEG1 (DEpressed Growth rate). Comparison of the deduced amino acid sequence of DEG1 with a protein sequence databank revealed homology with the enzyme tRNA pseudouridine synthase I of E. coli.
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  • 8
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    Current genetics 19 (1991), S. 9-14 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Mevalonate kinase ; Ergosterol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nucleotide sequence of the ERG12 gene, encoding mevalonate kinase, from Saccharomyces cerevisiae is presented. The longest open reading frame may code for a protein containing 443 amino acids with a deduced relative molecular mass of 48 500. The analysis of the nucleotide sequence reveals a complete identity with the yeast gene RAR1, isolated elsewhere by complementation of a rar1 mutation involved in the stability of plasmids with weak ARS. In addition, we show that mevalonate kinase is not a rate-limiting enzyme; however its sensitivity to FFP could be a key regulatory mechanism in the sterol pathway of yeast.
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  • 9
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    Applied physics 52 (1991), S. 213-217 
    ISSN: 1432-0630
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Mass spectroscopic studies of the neutral particles sputtered by Ar+ ions at 8 keV from polycrystaline samples have been performed, using non-resonant laser ionization and subsequent time-of-flight mass spectroscopy. Besides sputtered atoms, also dimer and trimer contributions in the order of 10−1 to 10−2 and 10−3 to 10−4, respectively, are found in the sputtered flux. The data obtained here together with previously published data by other groups for different bombarding energies provide strong support for the validity of the recombination model.
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  • 10
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    Applied physics 52 (1991), S. 445-447 
    ISSN: 1432-0630
    Keywords: 82.65 ; 36.40 ; 73.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Desorption of K atoms by laser-excitation of surface plasmons in small K particles is reported. The desorption rate has been measured for different laser wavelengths and particle sizes. Time-of-flight measurements reveal a kinetic energy of the desorbed atoms of Ekin=0.13(3) eV. From the experimental data it is concluded that the desorption mechanism is non-thermal in nature. Comparison of the results reported here with our earlier work on Na desorption is made.
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  • 11
    ISSN: 1432-0630
    Keywords: 36.40 ; 61.1.P ; 68.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Fullerene powder mixtures with different C60/C70 ratios have been analyzed by a variety of techniques, and results have been compared. The fullerence mixtures have been characterized as solutions in n-hexane by high-pressure liquid chromatography (HPLC) and UV-VIS spectroscopy. Thin films of fullerenes on Au(111) have been prepared from the mixtures by sublimation. The sublimation process has been studied by simultaneous thermogravimetric and differential thermal analyses. Thin fullerene films on Au(111) have been investigated by scanning tunneling microscopy (STM). The STM images show primarily two types of ballshaped molecules arranged in a lattice with hexagonal symmetry (fcc(111) face, nearest neighbour distance: 1 nm). The two species differ in diameter. STM images of films made of mixtures of different C60/C70 ratios show that C70 molecules display a larger apparent diameter (0.8 nm) and corrugation than C60 molecules (0.7 nm). The C60/C70 ratios obtained by counting the corresponding molecular species in the STM images of the thin films are compared to the C60/C70 ratios determined by HPLC on hexane solutions of the mixtures. The observed differences might be explained by different rates of sublimation for the two species. The STM images reveal film defects (vacancies and boundaries) and dynamic processes (displacement of C70 molecules and vacancies). In films prepared to have a C60 coverage of less than one monolayer, stable structural units of the C60(111) surface consisting of three or seven C60 molecules are revealed by STM. Occasionally, substructure within individual fullerene molecules is observed.
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  • 12
    ISSN: 1432-0983
    Keywords: Glucoamylase ; Gene cloning ; Hormoconis resinae ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA coding for glucoamylase P of Hormoconis resinae was cloned using a synthetic oligonucleotide probe coding for a peptide fragment of the purified enzyme and polyclonal anti-glucoamylase antibodies. Nucleotide-sequence analysis revealed an open reading frame of 1848 base pairs coding for a protein of 616 amino-acid residues. Comparison with other fungal glucoamylase amino-acid sequences showed homologies of 37–48%. The glucoamylase cDNA, when introduced into Saccharomyces cerevisiae under the control of the yeast ADC1 promoter, directed the secretion of active glucoamylase P into the growth medium.
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  • 13
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Dynamin ; Mitochondria ; GTP binding protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The isolation and characterization of MGM1, and yeast gene with homology to members of the dynamin gene family, is described. The MGM1 gene is located on the right arm of chromosome XV between STE4 and PTP2. Sequence analysis revealed a single open reading frame of 902 residues capable of encoding a protein with an approximate molecular mass of 101 kDa. Loss of MGM1 resulted in slow growth on rich medium, failure to grow on non-fermentable carbon sources, and loss of mitochondrial DNA. The mitochondria also appeared abnormal when visualized with an antibody to a mitochondrial-matrix marker. MGM1 encodes a dynamin-like protein involved in the propagation of functional mitochondria in yeast.
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  • 14
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    Current genetics 20 (1991), S. 167-171 
    ISSN: 1432-0983
    Keywords: Glycolysis ; Repetitive elements τ/δ ; Promoter ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In this study we report on the complete nucleotide sequence of the yeast phosphoglycerate mutase gene (GPM1) and its essential 5′ and 3′ non-coding regions. The transcriptional start points were determined by S1-mapping and sequencing of a cDNA clone. Several sequences identified as important for transcriptional regulation in yeast promoters are present upstream of the transcription start point. 3′ to the coding region we sequenced a composite repetitive element which, apparently, originated from a recombination between a delta-and a tau-element. Finally, we mapped the GPM1 gene 13 cM distal to fas1 on chomosome XI.
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  • 15
    ISSN: 1432-0983
    Keywords: Growth control ; Genetic mapping ; Molecular cloning ; Nucleo-mitochondrial interaction ; Saccharomyces cerevisiae ; Viability of petites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The PEL1 gene of Saccharomyces cerevisiae is essential for the cell viability of mitochondrial petite mutants, for the ability to utilize glycerol and ethanol on synthetic medium, and for cell growth at higher temperatures. By tetrad analysis the gene was assigned to chromosome III, centromere proximal of LEU2. The PEL1 gene has been isolated and cloned by the complementation of a pel1 mutation. The molecular analysis of the chromosomal insert carrying PEL1 revealed that this gene corresponds to the YCL4W open reading frame on the complete DNA sequence of chromosome III. The putative Pel1 protein is characterized by a low molecular weight of approximately 17 kDa, a low codon adaptation index, and a high leucine content.
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  • 16
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Papaver somniferum L. ; ARS ; Mitochondrial DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The minimal fragment of mitochondrial DNA from Papaver somniferum L. (poppy) able to promote autonomous plasmid replication in the yeast Saccharomyces cerevisiae was sequenced. Sequence analysis of the 917-bp MK4/8 DNA fragment revealed a high AT content, and the presence of two 12-bp sequences differing from the ARS core consensus of S. cerevisiae only by a T and C insertion, respectively. The mitochondrial insert contains a further six 11-bp sequences with one mismatch to the S. cerevisiae core consensus, more then 20 related sequences with two base pair exchanges, numerous direct and inverted repeats, and many copies of a sequence motif called the ARS box. The original 4.2-kb mitochondrial DNA fragment, as well as the minimal 917-bp subfragment in vector pFL1-E (a variant of YIP5, lacking an origin of replication in yeast), were then tested for their ability to replicate autonomously in another fungus, Kluyveromyces lactis.
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  • 17
    ISSN: 1432-0983
    Keywords: 2-Oxoglutarate dehydrogenase ; Molecular cloning ; Saccharomyces cerevisiae ; Sequencing ; Suppressor ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activity of mitochondrial 2-oxoglutarate dehydrogenase in S. cerevisiae can be impaired either by the ogd1 or the kgd1 mutation. The OGD1 gene and two suppressor genes were isolated by complementation of the ogd1 mutant. The complementation of the kdg1 mutant by the OGD1 gene, an allelism test, and meiotic mapping, revealed that the ogd1 and kgd1 mutations are allelic. The two mutations were differentiated by the cloned suppressor gene which was able to partially complement ogd1, but not kgd1. The molecular analysis of the suppressor gene revealed its identity with the natural tRNA CAG Gln gene found in the upstream region of URA10.
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  • 18
    ISSN: 1432-0983
    Keywords: Yeast ; Saccharomyces cerevisiae ; Sporulation mutants ; Reporter genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reporter genes consisting of sporulation-specific promoters fused to lacZ were used as markers to monitor the sporulation pathway of the yeast Saccharomyces cerevisiae. Strains transformed with these lacZ gene fusions expressed β-galactosidase (assayable on plates using the substrate 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside, X-gal) in a sporulation-dependent manner. Mutagenesis experiments performed on transformed strains resulted in the recovery of a number of novel sporulation mutants. Three classes of mutants were obtained: those which overexpressed the reporter gene under sporulation conditions, those which did not express the gene under any conditions, and those which expressed the gene in vegetative cells not undergoing sporulation. On the basis of the blue colony-colour produced in the presence of X-gal these have been described as superblue, white, and blue vegetative mutants, respectively. These were further characterised using earlier reporter genes and other marker systems. This study established that the multicopy reporter plasmids chosen do not interfere with sporulation; they are valid tools for monitoring the pathway and they provide a way to isolate mutations not readily selected by other markers.
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  • 19
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    Current genetics 24 (1993), S. 461-464 
    ISSN: 1432-0983
    Keywords: Chromosome fragmentation ; MEL gene family ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nine members, MEL2–MEL10, of the MEL gene family coding for α-galactosidase were physically mapped to the ends of the chromosomes by chromosome fragmentation. Genetic mapping of the genes supported the location of all the MEL genes in the left arm of their resident chromosomes.
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  • 20
    ISSN: 1432-0983
    Keywords: Yeast ; Saccharomyces cerevisiae ; Transformation ; Plasmid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have compared a number of procedures for the transformation of whole cells of the yeast Saccharomyces cerevisiae and assessed the effects of dimethylsulphoxide (DMSO) or ethanol, both of which have been reported to enhance transformation efficiency. We find that simplified methods benefit from the addition of one of these compounds, and although differences are observed between strains as to the more beneficial reagent, peak transformation efficiency is, in general obtained with 10% DMSO or 10% EtOH. Increases of between six- and 50-fold are observed, despite a reduction in cell viability, and at this concentration the two compounds are not additive in their effects. The optimum level appears to depend on a balance between improved DNA uptake and reduced cell viability. As a result of this work we present a straightforward and rapid transformation procedure.
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  • 21
    ISSN: 1432-0789
    Keywords: Antifungal activity ; Saccharomyces cerevisiae ; Phytopathogenic fungi ; Heterocyclic non-protein amino acid ; Pisum sativum ; Constitutive plant defence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary β-(Isoxazolin-5-on-2-yl)-alanine (βIA), a heterocyclic non-protein amino acid from root extracts and root exudates of pea seedlings, acts as a potent growth inhibitor of several eukaryotic organisms, including yeasts, phytopathogenic fungi, unicellular green algae, and higher plants. The antibiotic effect on baker's yeast was reversed by l-methionine, l-cysteine, and l-homocysteine. Phytopathogenic fungi such as Botrytis cinerea, Pythium ultimum, and Rhizoctonia solani grown on agar containing βIA were inhibited in the growth of mycelia or in the production of sclerotia. In contrast, no significant inhibition of either Gram-positive or Gram-negative bacteria was observed. Rhizobium leguminosarum, the compatible microsymbiont of Pisum spp., and Rhizobium meliloti were able to tolerate up to 2.9 mM βIA (500 ppm) without any effect on the growth rate. Bradyrhizobium japonicum even gave a positive chemotactic response to βIA. The ecological significance of βIA as a preformed plant protectant during the seedling stage of Pisum spp. and other βIA-containing legumes is discussed.
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  • 22
    ISSN: 1432-0983
    Keywords: Glycosylphosphatidylinositol anchored-protein ; Southern analysis ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The GGP1 gene encodes the only GPI-anchored glycoprotein (gp115) that has been purified todate in the budding yeast Saccharomyces cerevisiae. It is a single-copy gene whose deduced amino-acid sequence shares no significant homology to any other known protein. In this paper we report a Southern hybridization analysis of genomic DNA from different eukaryotic organisms to identify homologues of the GGP1 gene. We have analyzed DNA prepared from a unicellular green alga (Chlamydomonas eugametos), from two distantly related yeast species (Candida cylindracea and Schizosaccharomyces pombe), and from the common bean Phasoleus vulgaris. The moderate stringency of the experimental conditions and the high specificity of the probes used indicate that a single-copy of GGP1-related sequences exists in all these eukaryotic organisms. The chromosomal localization of the GGP1 gene in S. cerevisiae has also been determined.
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  • 23
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    Current genetics 23 (1993), S. 92-94 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Gene mapping ; Idiomorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The STA2 (glucoamylase) gene of Saccharomyces cerevisiae has been mapped close to the end of the left arm of chromosome II. Meiotic analysis of a cross between a haploid strain containing STA2, and another strain carrying the melibiase gene MEL1 (which is known to be at the end of the left arm of chromosome II) produced parental ditype tetrads only. Since there is no significant DNA sequence similarity between the STA2 and MEL1 genes, or their respective flanking regions, we conclude that these two genes are carried by separate non-hybridizing sequences of chromosomal DNA, either of which can reside at the end of the left arm of chromosome II. By analogy with the mating-type locus of Neurospora crassa, we suggest that the STA2 and MEL1 genes are idiomorphs with respect to one another.
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  • 24
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Phospholipid synthesis ; Phospholipid-N-methyltransferase ; Mutant ; Over-expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By functional complementation of the auxotrophic requirements for choline of a cdg1, cho2 double-mutant, by transformation with a genomic DNA library in a high copy number plasmid, two different types of complementing DNA inserts were identified. One type of insert was earlier shown to represent the CHO2 structural gene. In this report we describe the molecular and biochemical characterization of the second type of complementing activity. The transcript encoded by the cloned gene was about 1000-nt in length and was regulated in response to the soluble phospholipid precursors, inositol and choline. A gene disruption resulted in no obvious growth phenotype at 23°C or 30°C, but in a lack of growth at 37°C in the presence of monomethylethanolamine. Null-mutants exhibited an inositol-secretion phenotype, indicative of mutations in the lipid biosynthetic pathway. Complementation analysis, biochemical analysis of the phospholipid methylation pathway in vivo, and comparison of the restriction pattern of the cloned gene to published sequences, unequivocally identified the cloned gene as the OPI3 gene, encoding phospholipid-N-methyltransferase in yeast. When present in multiple copies the OPI3 gene efficiently suppresses the phospholipid methylation defect of a cho2 mutation. As a result of impaired synthesis of phosphatidylcholine, the INO1-deregulation phenotype is abolished in cho2 mutants transformed with the OPI3 gene on a high copy number plasmid. Taken together, these data demonstrate a significantly overlapping specificity of the OPI3 gene product for three sequential phospholipid methylation reactions in the de novo Ptd-Cho biosynthetic pathway.
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  • 25
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    Current genetics 23 (1993), S. 181-183 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; c-myc epitope ; Fusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to facilitate the process of epitope-tagging of yeast proteins, we have constructed two Saccharomyces cerevisiae-Escherichia coli shuttle vectors that allow fusion of a sequence encoding an epitope of the human c-myc protein at the 3′ end of any gene. An example of the use of this technique is presented.
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  • 26
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    Current genetics 23 (1993), S. 295-304 
    ISSN: 1432-0983
    Keywords: Meiosis ; Meiotic recombination ; Saccharomyces cerevisiae ; REC114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four new meiotic recombination genes were previously isolated by selecting for mutations that rescue the meiotic lethality of rad52 spo13 strains. One of these genes, REC114, is described here, and the data confirm that REC114 is a meiosis-specific recombination gene with no detectable function in mitosis. REC114 is located on chromosome XIII approximately 4,9 cM from CIN4. The nucleotide sequence reveals an open reading frame of 1262 bp, consensus intron splice sites close to the 3′ end, and indicates that the second exon codes for only seven amino acids. In the promoter region, a URS1 consensus sequence (TGGGCGGCTA), identical to the URS1 found in the promoter of SPO16, is present 93 bp upstream of the translation start site. Northern-blot hybridization demonstrates that REC114 is transcribed only during meiosis and that it is not expressed in the absence of the IME1 gene product, even when IME2 is constitutively expressed.
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  • 27
    ISSN: 1432-0983
    Keywords: Trehalase ; Trehalose-6-P synthase ; cAMP mutants ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rise in cAMP level that follows the addition of glucose or 2,4-dinitrophenol (DNP) to stationaryphase cells of Saccharomyces cerevisiae was accompanied by a marked activation of trehalase (3-fold increase) and a concomitant deactivation of trehalose-6 phosphate synthase (50% of the basal levels). In glucose-grown exponential cells, which are deficient in glucose-induced cAMP signalling, the addition of glucose also prompted a decrease in trehalose-6 phosphate synthase, but had no effect on trehalase activity. Mutants defective in the RAS-adenylate cyclase pathway (ras1 ras2 bcy1 strain), as well as mutants containing greatly reduced protein kinase activity either cAMP-dependent (tpk w1 BCY1 strains) or cAMP-independent (tpk1 w1 bcy1 strains), were unable to show glucose- or DNP-induced trehalase activation but still displayed a clear decrease in trehalose-6 phosphate synthase activity upon addition of these compounds. These data suggest that the activity of trehalose-6 phosphate synthase, as opposed to that of trehalase, is not controlled by the cAMP signalling pathway “in vivo”. Trehalose-6 phosphate synthase was competitively inhibited by glucose (Ki=15 mM) and resulted unaffected by ATP in assays performed “in vitro”.
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  • 28
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    Current genetics 23 (1993), S. 375-381 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Isocitrate lyase ; Gene regulation ; Ethanol induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ICL1 gene encoding the isocitrate lyase from Saccharomyces cerevisiae was cloned and sequenced. A reading frame of 557 amino acids showing significant similarity to isocitrate lyases from seven other species could be identified. Construction of icl1 null mutants led to growth defects on C2 carbon sources while utilization of sugars or C3 substrates remained unaffected. Using an ICL1-lacZ fusion integrated at the ICL1 locus, a more than 200-fold induction of β-galactosidase activity was observed after growth on ethanol when compared with glucose-repressed conditions. A preliminary analysis of the ICL1 upstream region identified a 364-bp fragment necessary and sufficient for this regulatory phenotype. Sequence motifs also present in the upstream regions of co-regulated genes were found within this region.
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  • 29
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Gene amplification ; ADH4 ; CUP1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Primary gene amplification, i.e., mutation from one gene copy to multiple gene copies per genome, is important in genomic evolution, as a means of producing anti-cancer drug resistance, and is associated with the progression of tumor malignancy. Primary amplification has not been studied in normal eukaryotic cells because amplifications are extremely rare in these cells. A system has been developed to phenotypically identify co-amplifications of the ADH4 and CUP1 genes of Saccharomyces cerevisiae and 21 independent spontaneous amplifications have been isolated.
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  • 30
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    Current genetics 23 (1993), S. 414-422 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Donation ; Gene conversion ; Double-strand break repair ; Heteroduplex DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have used transformation of yeast with lincarized plasmids to study the transfer of information to the unbroken chromosome during double-strand break repair. Using a strain which carried the wild-type HIS3 allele, and a linearized plasmid which carried a mutant his3 allele, we have obtained His- transformants. In these, double-strand break repair has resulted in precise transfer of genetic information from the plasmid to the chromosome. Such repair events, we suggest, are gene conversions which entail the formation of heteroduplex DNA on the (unbroken) chromosome. If this suggestion is correct, our results reflect the spatial distribution of such heteroduplex DNA. Transfer of information from the plasmid to the chromosome was obtained at a maximal frequency of 1.5% of the repair events, and showed a dependence with distance. Transformation to His- was also obtained with a 2-kbp insertion and with a deletion of 200 bp. The latter results suggest that gene conversion of large heterologies can occur via repair of a heteroduplex DNA intermediate.
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  • 31
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    Current genetics 24 (1993), S. 185-192 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Cell cycle ; Transcription ; DNA replication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In eukaryotic organisms, genes involved in DNA replication are often subject to some form of cell cycle control. In the yeast Saccharomyces cerevisiae, most of the DNA replication genes that have been characterized to date are regulated at the transcriptional level during G1 to S phase transition. A cis-acting element termed the MluI cell cycle box (or MCB) conveys this pattern of regulation and is common among more than 20 genes involved in DNA synthesis and repair. Recent findings indicate that the MCB element is well conserved among fungi and may play a role in controlling entry into the cell division cycle. It is evident from studies in higher systems, however, that transcriptional regulation is not the only form of control that governs the cell-cycle-dependent expression of DNA replication genes. Moreover, it is unclear why this general pattern of regulation exists for so many of these genes in various eukaryotic systems. This review summarizes recent studies of the MCB element in yeast and briefly discusses the purpose of regulating DNA replication genes in the eukaryotic cell cycle.
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  • 32
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    Current genetics 20 (1991), S. 189-194 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Bakers' and lager yeast ; Chromosomal and 2 μm DNA polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seven strains of bakers' yeast were obtained as a representative sample of the Spanish baking industry. The nuclear genome was monitored for polymorphism by transverse alternating field electrophoresis (TAFE) and restriction maps of 2 μm DNA were produced. All seven strains were uniquely different when evaluated by their total chromosomal lengths whereas only two 2 μm variants were defined. There was no apparent correlation between chromosomal and plasmid polymorphism. The extensive chromosomal polymorphism within one 2 μm DNA type indicates the rapid and relatively recent evolution of the nuclear genome. The hybrid origin (S. cerevisiae-S.monacensis) of lager yeast was critically evaluated by TAFE analysis of S. cerevisiae and S. carlsbergensis chromosomes. The absence of corresponding S. cerevisiae chromosomes III and XIII in S. carlsbergensis argued against the hybrid origin of lager strains. We discuss limitations of the hybrid origin hypothesis of industrial yeasts and propose that the molecular coevolution observed in 2 μm DNA serves as a useful additional mechanism for rationalization of some of the structural polymorphism of the nuclear genome.
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  • 33
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    Current genetics 20 (1991), S. 437-439 
    ISSN: 1432-0983
    Keywords: Schizosaccharomyces pombe ; Saccharomyces cerevisiae ; β-glucuronidase ; Colony colour assay ; Fluorometric assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Expression of the β-galactosidase gene in yeast has served as a screening marker for many purposes. Here it is shown that in two yeasts, Saccharomyces cerevisiae and Schizosaccharomyces pombe, the β-glucuronidase (GUS) gene can be used as an alternative marker. Since the histochemical substrate can not be taken up by yeast cells, direct colony screening of plates was found to be impossible. However, by a replica plating technique, GUS expression became visibly detectable within 10 min when the GUS gene was strongly expressed. The staining method could still be performed for expression at a 100-fold lower level, but incubation times of several hours were needed. Furthermore, specific GUS expression levels of yeast protein extracts could be quantified by a fluorometric assay which is both very simple to perform and highly sensitive. Since the GUS gene can also tolerate large N-terminal fusions, this method should be particularly attractive for studying such diverse problems as transcriptional and translational regulation or subcellular localization in yeast.
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  • 34
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Pentose-phosphate pathway ; Transketolase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Deletion mutants for the yeast transketolase gene TKL1 were constructed by gene replacement. Transketolase activity was below the level of detection in mutant crude extracts. Transketolase protein could be detected as a single protein band of the expected size by Western-blot analysis in wild-type strains but not in the delection mutant. Deletion of TKL1 led to a reduced but distinct growth in synthetic medium without an aromatic amino-acid supplement. We also isolated double and triple mutants for transketolase (tkl1), transaldolase (tal1), and glucose 6-phosphate dehydrogenase (zwf1) by crossing the different mutants. A tal1 tkl1 double mutant grew nearly like wild-type in rich medium. Only the tkl1 zwf1 double and the tal1 tkl1 zwf1 triple mutant grew more slowly than the wild-type in rich medium. This growth defect could be partly alleviated by the addition of xylulose but not ribose. The triple mutant still grew slowly on a synthetic mineral salts medium without a supplement of aromatic amino acids. This suggests the existence of an alternative but limited source of pentose phosphates and erythrose 4-phosphate in the tkl1 zwf1 double mutants. Hybridization with low stringency showed the existence of a sequence with homology to transketolase, possibly a second gene.
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  • 35
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    Current genetics 20 (1991), S. 181-184 
    ISSN: 1432-0983
    Keywords: Alpha amylase ; Secretion ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Extracellular glucoamylase activity was increased by a gene, which is present in super-secretor, but absent in low-secretor, strains of the yeast Saccharomyces cerevisiae. Genetic data indicated that this super-secretor gene is linked to the STA3 structural gene for glucoamylase. This gene appears to act specifically since it increased the secretion of glucoamylase but not of other secreted enzymes like acid phosphatase and invertase.
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  • 36
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Melibiose fermentation ; MEL ; Polymeric genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We used a combination of genetic hybridization analysis and electrokaryotyping with radioactively labelled MEL1 gene probe hybridization to isolate and identify seven polymeric genes for the fermentation of melibiose in strain CBS 5378 of Saccharomyces cerevisiae (syn. norbensis). Four of the MEL genes, i.e. MEL3, MEL4, MEL6 and MEL7, were allelic to those found in S. cerevisiae strain CBS 4411 (syn. S. oleaginosus) whereas three genes, i.e. MEL8, MEL9 and MEL10 occupied new loci. Electrokaryotyping showed that all seven MEL genes in CBS 5378 were located on different chromosomes. The new MEL8, MEL9 and MEL10 genes were found on chromosomes XV, X/XIV and XII, respectively.
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  • 37
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Ergosterol ; Squalene synthetase ; Yeast
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    Topics: Biology
    Notes: Summary The ERG9 gene of Saccharomyces cerevisiae has been cloned by complementation of the erg9-1 mutation which affects squalene synthetase. From the 5kkb insert isolated, the functional gene has been localized on a DNA fragment of 2.5 kb. The presence of squalene synthetase activity in E. coli bearing the yeast DNA fragment isolated, indicates that the structural gene encoding squalene synthetase has been cloned. The sequence of the 2.5 kb fragment contains an open reading frame which could encode a protein of 444 amino acids with a deduced relative molecular mass of 51 600. The amino acid sequence reveals one to four potential transmembrane domains with a hydrophobic segment in the C-terminal region. The N-terminus of the deduced protein strongly resembles the signal sequence of yeast invertase suggesting a specific mechanism of integration into the membranes of the endoplasmic reticulum.
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  • 38
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; β-phenethyl-alcohol ; ARO4 gene ; DAHP synthase
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    Topics: Biology
    Notes: Summary o-Fluoro-dl-phenylalanine (OFP)-resistant mutants which overproduce β-phenethyl-alcohol were isolated from a laboratory strain of Saccharomyces cerevisiae. Cells of one of the mutants accumulated tyrosine and phenylalanine 1.5–3 fold more than did wild-type cells. Its 3-deoxy-d-arabino-hepturosonate-7-phosphate (DAHP) synthase (EC 4.1.2.15), encoded by ARO4, was free from feedback inhibition by tyrosine. Genetic analysis revealed that the mutation was controlled by a single dominant gene, ARO4-OFP, encoding feedback-resistant DAHP synthase by tyrosine, and that this gene caused both the OFP resistance and β-phenethyl-alcohol overproduction. This was supported by molecular genetic studies using cloned ARO4 both from the wild-type and its mutant strain.
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  • 39
    ISSN: 1432-072X
    Keywords: Candida tropicalis ; Saccharomyces cerevisiae ; Peroxisomes ; Isocitrate lyase ; GAL7 promoter ; High level expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genomic DNA of peroxisomal isocitrate lyase (ICL) isolated from an n-alkane-assimilating yeast, Candida tropicalis, was truncated to utilize the original open reading frame under the control of the GAL7 promoter and was expressed in Saccharomyces cerevisiae. The recombinant ICL was synthesized as a functionally active enzyme with a specific activity similar to the enzyme purified from C. tropicalis, and was accounted for approximately 30% of the total extractable proteins in the yeast cells. This recombinant enzyme was easily purified to homogeneity. N-Terminal amino acid sequence, molecular masses of native form and subunit, amino acid composition, peptide maps, and kinetic parameters of the recombinant ICL were essentially the same as those of ICL purified from C. tropicalis. From these facts, S. cerevisiae was suggested to be an excellent microorganism to highly express the genes encoding peroxisomal proteins of C. tropicalis.
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  • 40
    ISSN: 1432-072X
    Keywords: Saccharomyces cerevisiae ; Pyruvate decarboxylase ; Pyruvate kinase ; Signalling ; Glycolysis mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pyruvate decarboxylase, PDCase, activity in wild-type yeast cells growing on ethanol is quite low but increases up to tenfold upon addition of glucose, less with galactose and only slightly with glycerol. PDCase levels in glycolysis mutant strains growing on ethanol or acetate were higher than in the wild-type strain. These levels correlated with the sum of the concentrations of three-carbon glycolytic metabolites. The highest accumulation was observed in a fructose bisphosphate aldolase deletion mutant concomintant with the highest PDCase activity wild-type level. On the other hand, the PDCase levels in the different mutants again correlated with the sum of the concentrations of the three-carbon glycolytic metabolites. This was interpreted to mean that full induction of PDCase activity requires the accumulation of hexose-and triosephosphates.
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  • 41
    ISSN: 1432-072X
    Keywords: Saccharomyces cerevisiae ; Acetyl-CoA ; l-Lysine N6 ; acetytransferase ; Lysine catabolism
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    Topics: Biology
    Notes: Abstract The carbon catabolism of l-lysine starts in Saccharomyces cerevisiae with acetylation by an acetyl-CoA: l-lysine N6-acetyltransferase. The enzyme is strongly induced in cells grown on l-lysine as sole carbon source and has been purified about 530-fold. Its activity was specific for acetyl-CoA and, in addition to l-lysine, 5-hydroxylysine and thialysine act as acetyl acceptor. The following apparent Michaelis constants were determined: acetyl-CoA 0.8 mM, l-lysine 5.8 mM, dl-5-hydroxylysine 2.8 mM, l-thialysine 100 mM. The enzyme had a maximum activity at pH 8.5 and 37°C. Its molecular mass, estimated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, was 52 kDa. Since the native molecular mass, determined by gel filtration, was 48 kDa, the enzyme is a monomer.
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  • 42
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    Archives of microbiology 156 (1991), S. 38-42 
    ISSN: 1432-072X
    Keywords: Water stress ; Saccharomyces cerevisiae ; Glycerol ; Yeast water relations ; Osmoregulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When exponentially growing Saccharomyces cerevisiae was transferred from a normal high water activity growth medium (aw 0.997) to a medium containing 8% NaCl low water activity growth medium (aw 0.955), glycerol accumulation during the first eight hours of the adaptation was both retarded and greatly diminished in magnitude. Investigation of the underlying reasons for the slow onset of glycerol accumulation revealed that not only was overall glycerol production reduced by salt transfer, but also the rates of ethanol production and glucose consumption were reduced. Measurement of glycolytic intermediates revealed an accumulation of glucose-6-phosphate, fructose-6-phosphate, fructose 1,6 bisphosphate and phosphoenolpyruvate in S. cerevisiae 3 to 4 h after transfer to salt, suggesting that one or more glycolytic enzymes were inhibited. Potassium ions accumulated in S. cerevisiae after salt transfer and reached a maximum about 6 h after transfer, whereas the sodium ion content increased progressively during the adaptation period. The trehalose content also increased in adapting cells. It is suggested that inhibition of glycerol production during the initial period of adaptation could be due to either the inhibition of glycerol-3-phosphate dehydrogenase by increased cation content or the inhibitin of glycolysis, glycerol being produced glycolytically in S. cerevisiae. The increased accumulation of glycerol towards the end of the 8-h period suggests that the osmoregulatory response of S. cerevisiae involves complex sets of adjustments in which inhibition of glycerol-3-phosphate dehydrogenase must be relieved before glycerol functions as a major osmoregulator.
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  • 43
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    Molecular and cellular biochemistry 124 (1993), S. 131-140 
    ISSN: 1573-4919
    Keywords: Schizosaccharomyces pombe ; Saccharomyces cerevisiae ; H+-ATPase ; intracellular pH ; carboxy-seminaphthorhodafluor-1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We examined cytoplasmic pH regulation inSchizosaccharomyces pombe andSaccharomyces cerevisiae using pH-sensitive fluorescent dyes. Of several different fluorescent compounds tested, carboxy-seminaphthorhodafluor-1 (C.SNARF-1) was the most effective. Leakage of C.SNARF-1 fromS. pombe was much slower than leakage fromC. cerevisiae. Using the pH-dependent fluorescence of C.SNARF-1 we showed that at an external pH of 7, mean resting internal pH was 7.0 forS. pombe and 6.6 forS. cerevisiae. We found that internal pH inS. pombe was maintained over a much narrower range in response to changes in external pH, especially at acidic pH. The addition of external glucose caused an intracellular alkalinization in both species, although the effect was much greater inS. cerevisiae than inS. pombe. The plasma membrane H+-ATPase inhibitor diethylstilbestrol reduced both the rate and extent of alkalinisation, with an IC50 of approximately 35 μM in both species. Amiloride also inhibited internal alkalinisation with IC50's of 745 μM forS. cerevisiae and 490 μM forS. pombe.
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  • 44
    ISSN: 1573-4919
    Keywords: glutathione reductase ; Saccharomyces cerevisiae ; redox interconversion ; metals ; cell-free extracts
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    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Redox inactivation of glutathione reductase involves metal cations, since chelators protected against NADPH-inactivation, 3 µM EDTA or 10 µM DETAPAC yielding full protection. Ag+, Zn2+ and Cd2+ potentiated the redox inactivation promoted by NADPH alone, while Cr3+, Fe2+, Fe3+, Cu+, and Cu2+ protected the enzyme. The Zn2+ and Cd2+ effect was time-dependent, unlike conventional inhibition. Glutathione reductase interconversion did not require dioxygen, excluding participation of active oxygen species produced by NADPH and metal cations. One Zn2+ ion was required per enzyme subunit to yield full NADPH-inactivation, the enzyme being reactivated by EDTA. Redox inactivation of glutathione reductase could arise from the blocking of the dithiol formed at the active site of the reduced enzyme by metal cations, like Zn2+ or Cd2+. The glutathione reductase activity of yeast cell-free extracts was rapidly inactivated by low NADPH or moderate NADH concentrations; NADP+ also promoted rapid inactivation in fresh extracts, probably after reduction to NADPH. Full inactivation was obtained in cell-free extracts incubated with glucose-6-phosphate or 6-phosphogluconate; the inactivating efficiency of several oxidizable substrates was directly proportional to the specific activities of the corresponding dehydrogenases, confirming that redox inactivation derives from NADPH formed in vitro.
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  • 45
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    Plant molecular biology 22 (1993), S. 1177-1180 
    ISSN: 1573-5028
    Keywords: abscisic acid ; developmental regulation ; heat shock proteins ; Oryza sativa ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Antibodies raised against yeast heat shock protein (HSP) 104 recognized a heat-inducible polypeptide with a molecular mass of 110 kDa in shoot tissue of young rice seedlings. Root tissue of the same age showed no immuno-reaction with yeast HSP 104 antibodies. The 110 kDa polypeptide of rice was also shown to be abscisic acid-inducible in young seedlings. Though this polypeptide was seen to be constitutively present in the flag leaf of 90-day-old field-grown plant, it was not much affected by either heat shock or abscisic acid in this case.
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  • 46
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    Journal of fluorescence 3 (1993), S. 241-244 
    ISSN: 1573-4994
    Keywords: Killer toxin K1 ; bromocresol purple staining ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Optimal assay conditions were established for the previously described method used to determine the activity ofSaccharomyces cerevisiae pore-forming killer toxin K1. The method is based on cell staining with bromocresol purple. Sensitive cells ofS. cerevisiae from the early exponential phase under nongrowth conditions and in the presence of glucose were the most convenient for determining the killer toxin activity. Maximum killing war reached when the suspension was buffered with 10 mM citrate-phosphate at pH 4.6.
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  • 47
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Ribosomal protein genes ; Transcription activation ; cAMP ; Growth control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rate of ribosomal protein gene (rp-gene) transcription in yeast is accurately adjusted to the cellular requirement for ribosomes under various growth conditions. However, the molecular mechanisms underlying this co-ordinated transcriptional control have not yet been elucidated. Transcriptional activation of rp-genes is mediated through two different multifunctional trans-acting factors, ABF1 and RAP1. In this report, we demonstrate that changes in cellular rp-mRNA levels during varying growth conditions are not parallelled by changes in the in vitro binding capacity of ABF1 or RAP1 for their cognate sequences. In addition, the nutritional upshift response of rp-genes observed after addition of glucose to a culture growing on a non-fermentative carbon source turns out not to be the result of increased expression of the ABF1 and RAP1 genes or of elevated DNA-binding activity of these factors. Therefore, growth rate-dependent transcription regulation of rp-genes is most probably not mediated by changes in the efficiency of binding of ABF1 and RAP1 to the upstream activation sites of these genes, but rather through other alterations in the efficiency of transcription activation. Furthermore, we tested the possibility that cAMP may play a role in elevating rp-gene expression during a nutritional shift-up. We found that the nutritional upshift response occurs normally in several mutants defective in cAMP metabolism.
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  • 48
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; UV damage ; Mating type ; Inducible repair
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    Topics: Biology
    Notes: Abstract The prior UV irradiation of α haploid Saccharomyces cerevisiae with a UV dose of 25 J/m2 substantially increases the repairability of damage subsequently induced by a UV dose of 70 J/m2 given 1 h after the first irradiation. This enhancement of repair is seen at both the MATa and HMLα loci, which are, respectively, transcriptionally active and inactive in α haploid cells. The presence in the medium of the protein synthesis inhibitor, cycloheximide in the period between the two irradiations eliminated this effect. Enhanced repair still occurred if cycloheximide was present only after the final UV irradiation. This indicated that the first result is not due to cycloheximide merely blocking the synthesis of repair enzymes associated with a hypothetical rapid turnover of such molecules. The enhanced repairability is not the result of changes in chromatin accessibility without protein synthesis, merely caused by the repair of the damage induced by the prior irradiation. The data clearly show that a UV-inducible removal of pyrimidine dimers has occurred which involves the synthesis of new proteins. The genes known to possess inducible promoters, and which are involved in excision are RAD2, RAD7, RAD16 and RAD23. Studies with the rad7 and rad16 mutants which are defective in the ability to repair HMLα and proficient in the repair' of MATα showed that in rad7, preirradiation enhanced the repair at MATα, whereas in rad16 this increased repair of MATα was absent. The preirradiation did not modify the inability to repair HMLα in either strain. Thus RAD16 has a role in this inducible repair. Inducible repair is also absent in a rad2 strain which cannot repair MATα or HMLα after a single UV dose.
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  • 49
    ISSN: 1573-4943
    Keywords: Screening protein structures ; electroblotting ; glucose-6-phosphate dehydrogenase ; Saccharomyces cerevisiae ; Pichia jadinii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Rapid assessment of structural relationships between yeast glucose-6-phosphate dehydrogenases and other eukaryotic types of this enzyme is described. Separation and size estimation of large fragments by sodium dodecylsulfate/polyacrylamide gel electrophoresis, electroblotting onto disks, and sequencer analysis provide data that permit alignment of the segments thus characterized with the related proteins, and utilize existing structural knowledge to assess new enzyme structures. Affinity labeling allows further correlations. The results establish the overall structural arrangements of the new proteins, including the location of the active-site lysine residue, even though the yeast enzyme structures are found to differ markedly from the few previously characterized glucose-6-phosphate dehydrogenases.
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  • 50
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    Molecular genetics and genomics 230 (1991), S. 241-250 
    ISSN: 1617-4623
    Keywords: Yeast ; Saccharomyces cerevisiae ; Adenylyl cyclase ; CDC25 ; RAS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The TFS1 gene of Saccharomyces cerevisiae is a dosage-dependent suppressor of cdc25 mutations. Overexpression of TFS1 does not alleviate defects of temperature-sensitive adenylyl cyclase (cdc35) or ras2 disruption mutations. The ability of TFS1 to suppress cdc25 is allele specific: the temperature-sensitive cdc25-1 mutation is suppressed efficiently but the cdc25-5 mutation and two disruption mutations are only partially suppressed. TFS1 maps to a previously undefined locus on chromosome XII between RDN1 and CDC42. The DNA sequence of TFS1 contains a single long open reading frame encoding a 219 amino acid polypeptide that is similar in sequence to two mammalian brain proteins. Insertion and deletion mutations in TFS1 are haploviable, indicating that TFS1 is not essential for growth.
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  • 51
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Sodium efflux ; Lithium efflux ; ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ENA2 gene encoding a P-type ATPase involved in Na+ and Li+ effluxes in Saccharomyces cerevisiae has been isolated. The putative protein encoded by ENA2 differs only in thirteen amino acids from the protein encoded by ENA1/PMR2. However, ENA2 has a very low level of expression and for this reason did not confer significant Li+ tolerance on a Li+ sensitive strain. ENA1 and ENA2 are the first two units of a tandem array of four highly homologous genes with probably homologous functions.
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  • 52
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    Molecular genetics and genomics 237 (1993), S. 375-384 
    ISSN: 1617-4623
    Keywords: Regulation of meiosis ; Saccharomyces cerevisiae ; IME1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The IME1 gene of Saccharomyces cerevisiae is required for initiation of meiosis. Transcription of IME1 is detected under conditions which are known to induce initiation of meiosis, namely starvation for nitrogen and glucose, and the presence of MATa1 and MATα2 gene products. In this paper we show that IME1 is also subject to translational regulation. Translation of IME1 mRNA is achieved either upon nitrogen starvation, or upon G1 arrest. In the presence of nutrients, constitutively elevated transcription of IME1 is also sufficient for the translation of IME1 RNA. Four different conditions were found to cause expression of Imel protein in vegetative cultures: elevated transcription levels due to the presence of IME1 on a multicopy plasmid; elevated transcription provided by a Gal-IME1 construct; G1 arrest due to α-factor treatment; G1 arrest following mild heat-shock treatment of cdc28 diploids. Using these conditions, we obtained evidence that starvation is required not only for transcription and efficient translation of IME1, but also for either the activation of Ime1 protein or for the induction/activation of another factor that, either alone or in combination with Ime1, induces meiosis.
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  • 53
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Transcription ; spt mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mutations in the SPT4 gene of Saccharomyces cerevisiae were isolated as suppressors of δ insertion mutations that interfere with adjacent gene transcription. Recent genetic evidence indicates that the SPT4 protein functions with two other proteins, SPT5 and SPT6, in some aspect of transcription initiation. In this work we have characterized the SPT4 gene and we demonstrate that spt4 mutations, like spt5 and spt6 mutations, cause changes in transcription. Using the cloned SPT4 gene, spt4 null mutations were constructed; in contrast to spt5 and spt6 null mutants, which are inviable, spt4 null mutants are viable and have an Spt− phenotype. The DNA sequence of the SPT4 gene predicts a protein product of 102 amino acids that contains four cysteine residues positioned similarly to those of zinc binding proteins. Mutational analysis suggests that at least some of these cysteines are essential for SPT4 function. Genetic mapping showed that SPT4 is a previously unidentified gene that maps to chromosome VII, between ADE6 and CLY8.
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  • 54
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    Molecular genetics and genomics 237 (1993), S. 463-466 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; cyrl-2 ; Nonsense mutation ; CAMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary cyrl-2 is a temperature-sensitive mutation of the yeast adenylate cyclase structural gene, CYR1. The cyrl-2 mutation has been suggested to be a UGA mutation since a UGA suppressor SUP201 has been isolated as a suppressor of the cyrl-2 mutation. Construction of chimeric genes restricted the region containing the cyrl-2 mutation, and the cyrl-2 UGA mutation was identified at codon 1282, which lies upstream of the region coding for the catalytic domain of adenylate cyclase. Alterations in the region upstream of the cyrl-2 mutation site result in null mutations. The complete open reading frame of the cyrl-2 gene expressed under the control of the GAL1 promoter complemented cyrl-dl in a galactose-dependent manner. These results suggest that at the permissive temperature weak readthrough occurs at the cyrl-2 mutation site to produce low levels of active adenylate cyclase. An endogenous suppressor in yeast cells is assumed to be responsible for this readthrough.
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  • 55
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    Molecular genetics and genomics 238 (1993), S. 6-16 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; cAMP MKS1 ; GAL11
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to isolate genes that function downstream of the Ras-cAMP pathway in Saccharomyces cerevisiae, a YEp13-based genomic library was screened for clones that inhibit growth of cells with diminished A-kinase activity. One such gene, MKS1, was found to encode a hydrophilic 52 kDa protein that shares weak homology with the yeast SPT2/SIN1 gene product. Three lines of evidence suggest that the MKS1 gene product is a negative regulator downstream of the Ras-cAMP pathway: (i) overexpression of MKS1 inhibits growth of cyrl disruptant cells on YPD medium containing a low concentration of cAMP; (ii) overexpression of MKS1 does not affect TPK1 expression; and (iii) the temperature-sensitive cyrl-230 mutation is partially suppressed by mks1 disruption. The mks1 mutant shows similar phenotypes to gal11/spt13, i.e., it cannot grow on YPGal containing ethidium bromide at 25°C, or on YPGly or SGal at 37°C. The mks1 gal11 double mutant shows more marked phenotypic changes than the single mutants. These results suggest that MKS1 is involved in transcriptional regulation of several genes by cAMP.
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  • 56
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    Molecular genetics and genomics 240 (1993), S. 36-42 
    ISSN: 1617-4623
    Keywords: Yeast ; Saccharomyces cerevisiae ; DNA synthesis genes ; Cell cycle regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two mutants have been isolated in Saccharomyces cerevisiae in which transcripts from at least CDC8, CDC9, CDC21 (TMP1) and POL1 genes are expressed constitutively in cells blocked at START by use of either α-pheromone or the cdc28 mutation. The transcripts from these genes also persist in mutant stationary phase cells; however, cell cycle regulation of these four DNA synthesis genes occurs normally in late G1. The mutation therefore does not appear to lie in the MCB-DSC1 (MBF) system that controls the periodic regulation of the genes, but must affect some control mechanism regulating basal levels of expression.
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  • 57
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    Molecular genetics and genomics 226 (1991), S. 224-232 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; SAM1 and SAM2 genes ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary S-adenosyl-l-methionine (AdoMet) is synthesized by transfer of the adenosyl moiety of ATP to the sulfur atom of methionine. This reaction is catalysed by AdoMet synthetase. In all eukaryotic organisms studied so far, multiple forms of AdoMet synthetases have been reported and from their recent study, it appears that AdoMet synthetase is an exceptionally well conserved enzyme through evolution. In Saccharomyces cerevisiae, we have demonstrated the existence of two AdoMet synthetases encoded by genes SAM1 and SAM2. Yeast, which is able to concentrate exogenously added AdoMet, is thus a particularly useful biological system to understand the role and the physiological significance of the preservation of two almost identical AdoMet synthetases. The analysis of the expression of the two SAM genes in different genetic backgrounds during growth under different conditions shows that the expression of SAM1 and SAM2 is regulated differently. The regulation of SAM1 expression is identical to that of other genes implicated in AdoMet metabolism, where as SAM2 shows a specific pattern of regulation. A careful analysis of the expression of the two genes and of the variations in the methionine and AdoMet intracellular pools during the growth of different strains lead us to postulate the existence of two different AdoMet pools, each one suppplied by a different AdoMet synthetase but in equilibrium with each other. This could be a means of storing AdoMet whenever this metabolite is overproduced, thus avoiding the degradation of a metabolite the synthesis of which is energetically expensive.
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  • 58
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Calmodulin-binding protein ; Protein phosphatase (2B type) ; Calcineurin A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Saccharomyces cerevisiae genomic clones that encode calmodulin-binding proteins were isolated by screening a λgt11 expression library using125I-labeled calmodulin as probe. Among the cloned yeast genes, we found two closely related genes (CMP1 andCMP2) that encode proteins homologous to the catalytic subunit of phosphoprotein phosphatase. The presumed CMP1 protein (62999 Da) and CMP2 protein (68496 Da) contain a 23 amino acid sequence very similar to those identified as calmodulin-binding sites in many calmodulin-regulated proteins. The yeast genes encode proteins especially homologous to the catalytic subunit of mammalian phosphoprotein phosphatase type 213 (calcineurin). The products of theCMP1 andCMP2 genes were identified by immunoblot analysis of cell extracts as proteins of 62000 and 64000 Da, respectively. Gene disruption experiments demonstrated that elimination of either or both of these genes had no effect on cell viability, indicating that these genes are not essential for normal cell growth.
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  • 59
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; recA gene expression ; Resistance to ionizing and ultraviolet radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Escherichia coli recA protein coding region was ligated into an extrachromosomally replicating yeast expression vector downstream of the yeast alcohol dehydrogenase promoter region to produce plasmid pADHrecA. Transformation of the wild-type yeast strains YNN-27 and 7799-4B, as well as the recombination-deficient rad52-t C5-6 mutant, with this shuttle plasmid resulted in the expression of the bacterial 38 kDa RecA protein in exponential phase cells. The wild-type YNN27 and 7799-4B transformants expressing the bacterial recA gene showed increased resistance to the toxic effects of both ionizing and ultraviolet radiation. RecA moderately stimulated the UV-induced mutagenic response of 7799-4B cells. Transformation of the rad52-t mutant with plasmid pADHrecA did not result in the complementation of sensitivity to ionizing radiation. Thus, the RecA protein endows the yeast cells with additional activities, which were shown to be error-prone and dependent on the RAD52 gene.
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  • 60
    ISSN: 1617-4623
    Keywords: Fungi ; Saccharomyces cerevisiae ; Zinc ; Processing ; Pro region
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The neutral protease II (NpII) from Aspergillus oryzae is a zinc-containing metalloprotease with some unique properties. To elucidate its structure, we isolated a full-length cDNA clone for NpII. Sequence analysis reveals that NpII has a prepro region consisting of 175 amino acids preceding the mature region, which consists of 177 amino acids. As compared with other microbial metalloproteases, NpII is found to be unique in that it shares only a limited homology with them around two zinc ligand His residues and that the positions of the other zinc ligand (Glu) and the active site (His) cannot be established by homology. When a plasmid designed to express the prepro NpII cDNA was introduced into Saccharomyces cerevisiae and the transformant was cultured in YPD medium (2% glucose, 2% polypeptone, 1% yeast extract), it secreted a proNpII. However, in a culture of the same medium containing 0.2 mM ZnCl2, it secreted a mature NpII with a specific activity and N-terminus identical to those of native NpII. This observation suggests that either an autoproteolytic activity or a yeast protease effected the processing.
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  • 61
    ISSN: 1617-4623
    Keywords: Ricin ; Toxin ; Mutant ; Saccharomyces cerevisiae ; Expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Yeast transformants containing integrated copies of a galactose-regulated, ricin toxin A chain (RTA) expression plasmid were constructed and used in an attempt to isolate RTA-resistant yeast mutants. Analysis of RNA from mutant strains demonstrated that approximately half contained ribosomes that had been partially modified by RTA, although all the strains analysed transcribed full-length RTA RNA. The mutant strains could have mutations in yeast genes giving rise to RTA-resistant ribosomes or they could contain alterations within the RTA-encoding DNA causing production of mutant toxin. Ribosomes isolated from mutant strains were shown to be susceptible to RTA modification in vitro suggesting that the strains contain alterations in RTA. This paper describes the detailed analysis of one mutant strain which has a point mutation that changes serine 203 to asparagine in RTA protein. Although serine 203 lies outside the proposed active site of RTA its alteration leads to the production of RTA protein with a greatly reduced level of ribosome modifying activity. This decrease in activity apparently allows yeast cells to survive expression of RTA as only a proportion of the ribosomes become modified. We demonstrate that the mutant RTA preferentially modifies 26S rRNA in free 60S subunits and has lower catalytic activity compared with native RTA when produced in Escherichia coli. Such mutations provide a valuable means of identifying residues important in RTA catalysis and of further understanding the precise mechanism of action of RTA.
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  • 62
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; CTP synthetase ; Pyrimidine pathway ; Intracellular pyrimidine pool ; Non-essential gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The URA7 gene of Saccharomyces cerevisiae encodes CTP synthetase (EC 6.3.4.2) which catalyses the conversion of uridine 5′-triphosphate to cytidine 5′-triphosphate, the last step of the pyrimidine biosynthetic pathway. We have cloned and sequenced the URA 7 gene. The coding region is 1710 by long and the deduced protein sequence shows a strong degree of homology with bacterial and human CTP synthetases. Gene disruption shows that URA7 is not an essential gene: the level of the intracellular CTP pool is roughly the same in the deleted and the wild-type strains, suggesting that an alternative pathway for CTP synthesis exists in yeast. This could involve either a divergent duplicated gene or a different route beginning with the amination of uridine mono- or diphosphate.
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  • 63
    ISSN: 1617-4623
    Keywords: Heat shock response ; HSP70 ; Saccharomyces cerevisiae ; RAS-CAMP pathway ; Multicopy suppressor of ira1
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    Topics: Biology
    Notes: abstract The MSI3 gene was isolated as a multicopy suppressor of the heat shock-sensitive phenotype of the iral mutation, which causes hyperactivation of the RAS-cAMP pathway. Overexpression of MSI3 also suppresses the heat shock-sensitive phenotype of the bcyl mutant. Determination of the DNA sequence of MSI3 revealed that MSI3 can encode a 77.4 kDa protein related to the HSP70 family. The amino acid sequence of Msi3p is about 30% identical to that of the Ssalp of Saccharomyces cerevisiae. This contrasts with the finding that members of the HSP70 family generally show at least 50% amino acid identity. The consensus nucleotide sequence of the heat shock element (HSE) was found in the upstream region of MSI3. Moreover, the steady-state levels of the MSI3 mRNA and protein were increased upon heat shock. These results indicate that the MSI3 gene encodes a novel HSP70-like heat shock protein. Disruption of the MSI3 gene was associated with a temperature sensitive growth phenotype but unexpectedly, thermotolerance was enhanced in the disruptant.
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  • 64
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    Molecular genetics and genomics 241 (1993), S. 657-666 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Pyruvate decarboxylase ; Transcription ; Glucose induction ; Autoregulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The regulatory gene PDC2 was identified in a screen for mutations affecting pyruvate decarboxylase activity in yeast. I have cloned and sequenced this gene. The predicted protein of 925 amino acids has no homology to any sequence in the databases. However, the protein sequence is rich in asparagine and serine residues, as is often found for transcriptional regulators. The PDC2 deletion mutant exhibits a phenotype very similar to, but more severe than that of the point mutant: a strongly reduced pyruvate decarboxylase specific activity, slow, respiration-dependent growth on glucose, and accumulation of pyruvate. The activity of other glycolytic enzymes seems to be unaffected by the pdc2Δ mutation. Synthesis of pyruvate decarboxylase is regulated by PDC2 at the transcriptional level. Expression of the major structural gene for pyruvate decarboxylase, PDC1, is strongly reduced in pdc2Δ mutants. Transcription of the generally more weakly expressed PDC5 gene appears to be entirely abolished. However, glucose induction of pyruvate decarboxylase synthesis is unaffected. Thus, PDC2 is either important for a high basal level of PDC gene expression or it plays a positive role in the autoregulation that controls expression of PDC1 and PDC5.
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  • 65
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    Molecular genetics and genomics 241 (1993), S. 680-684 
    ISSN: 1617-4623
    Keywords: Nitrogen mustard resistance ; Regulation of choline permease ; Co-regulation ; Phospholipid biosynthesis ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An 815 by region of the promoter of the Saccharomyces cerevisiae gene CTR/HNM1, encoding choline permease was sequenced and its regulatory function analysed by deletion studies in an in-frame promoter-lacZ construct. In addition to the TATA box, a 10 by motif (consensus 5′-CATGTGAAAT-3′) was found to be mandatory for CTR/HNM1 expression. This ‘decamer’ motif is located between nucleotides −262 and −271 and is identical in 9 of 10 by with the regulatory motif found in the S. cerevisiae INO1 and CHO1 genes. Constructs with the 10 by sequence show high constitutive expression, while elimination or alterations at three nucleotide positions, of the decamer motif in the context of an otherwise unchanged promoter leads to total loss of β-galactosidase production. Expression of the CTR/HNM1 gene in wild-type cells is regulated by the phospholipid precursors inositol and choline; no such influence is seen in cells bearing mutations in the phospholipid regulatory genes INO2, INO4, and OPI1. There is no regulation by INO2 and OPI1 in the absence of the decamer motif. However constructs not containing this sequence (promoter intact to positions −213 or −152) are still controlled by INO4. Other substrates of the choline permease, i.e. ethanolamine, nitrogen mustard and nitrogen half mustard do not regulate expression of CTR/HNM1.
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  • 66
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Lysyl-tRNA synthetase ; PMR2 repeat ; Genome organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary TheKRS1 gene encodes the cytoplasmic form ofSaccharomyces cerevisiae lysyl-tRNA synthetase. TheKRS1 locus has been characterized. The lysyl-tRNA synthetase gene is unique in the yeast genome. The gene is located on the right arm of chromosome IV and disruption of the open reading frame leads to lethality. These results contrast with the situation encountered inEscherichia coli where lysyl-tRNA synthetase is coded by two distinct genes,lysS andlysU, and further address the possible biological significance of this gene duplication. The nucleotide sequence of the 3′-flanking region has been established. It encodes a long open reading frame whose nucleotide and amino acid structures are almost identical toPMR2, a cluster of tandemly repeated genes coding for P-type ion pumps. The sequence alterations relative toPMR2 are mainly located at the C-terminus of the protein.
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  • 67
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; mRNA metabolism ; Nucleus
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary Mutations in the PRP20 gene of yeast show a pleiotropic phenotype, in which both mRNA metabolism and nuclear structure are affected. srm1 mutants, defective in the same gene, influence the signal transduction pathway for the pheromone response. The yeast PRP20/SRM1 protein is highly homologous to the RCC1 protein of man, hamster and frog. In mammalian cells, this protein is a negative regulator for initiation of chromosome condensation. We report the analysis of two, independently isolated, recessive temperature-sensitive prp20 mutants. They have identical G to A transitions, leading to the alteration of a highly conserved glycine residue to glutamic acid. By immunofluorescence microscopy the PRP20 protein was localized in the nucleus. Expression of the RCC1 protein can complement the temperature-sensitive phenotype of prp20 mutants, demonstrating the functional similarity of the yeast and mammalian proteins.
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  • 68
    ISSN: 1617-4623
    Keywords: Texas maize cytoplasmic male sterility ; Saccharomyces cerevisiae ; Mitochondria ; Image and flow cytometry ; 3,3′-Dihexyloxacarbocyanine iodide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The urf13TW gene, which is derived from the mitochondrial T-urf13 gene responsible for Texas cytoplasmic male sterility in maize, was expressed in Saccharomyces cerevisiae by targeting its translation product into mitochondria. Analysis by oxygraphy at the population level revealed that in the presence of methomyl the oxygen uptake of intact yeast cells carrying the targeted protein is strongly stimulated only with ethanol as respiratory substrate and not with glycerol, lactate, pyruvate, or acetate. When malate is the substrate oxidized by isolated mitochondria, interaction between the targeted protein and methomyl results in significant inhibition of oxygen uptake. This inhibition is eliminated and oxygen uptake is stimulated by subsequent addition of NAD+. Using 3,3′-dihexyloxacarbocyanine iodide [DiOC6(3)] as probe, interactive laser scanning and flow cytometry, which permit analysis at the individual cell level, demonstrated that specific staining of the mitochondrial compartment is obtained and that DiOC6(3) fluorescence serves as a measure of the membrane potential. Finally, it was shown that, as in T cytoplasm maize mitochondria, HmT toxin and methomyl dissipate the membrane potential of yeast mitochondria that carry the foreign protein. Furthermore, the results suggest that the HmT toxin and methomyl response is related to the plasmid copy number per cell and that the deleterious effect induced by HmT toxin is stronger than that of methomyl.
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  • 69
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Nuclear pet mutants ; Mitochondrial transcription ; Mutant RNA polymerase ; Specificity factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The temperature-sensitive yeast mutant pet-ts798 is characterized by an altered mitochondrial transcription apparatus. The mutation has previously been shown to map in the RP041 gene encoding the core enzyme of mitochondrial RNA polymerase. In the present study the rpo41/pet-ts798 allele was cloned and sequenced, demonstrating that the mutant phenotype is caused by a single amino acid change in a conserved region of the core polymerase. The nuclear gene MTF1, previously isolated as a high copy suppressor of mutant rpo41/pet-ts798, and its gene product were characterized in more detail. Import of a MTF1-COXIV fusion protein in vivo and also import studies with in vitro synthesized MTF1 precursors indicate that MTF1 is a mitochondrial protein and that no apparent cleavage occurs during its import into mitochondria. DNA-binding assays demonstrate that the MTF1 protein alone interacts with DNA in a non-specific manner. An antibody directed against specificity factor MTF1 was raised and used for immunological quantification experiments. The results indicate that suppression is mediated by an increased level of MTF1 protein in mitochondria of the rpo41/pet-ts798 mutant. Possible implications of this finding for the mechanism of suppression are discussed.
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    Molecular genetics and genomics 228 (1991), S. 335-344 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; DNA interstrand cross-links ; DNA repair ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The repair of interstrand cross-links induced by 8-methoxypsoralen plus UVA (365 nm) radiation DNA was analyzed in diploid strains of the yeast Saccharomyces cerevisiae. The strains employed were the wild-type D7 and derivatives homozygous for the rad18-1 or the rad3-12 mutation. Alkaline step-elution and electron microscopy were performed to follow the process of induction and removal of photoinduced crosslinks. In accordance with previous reports, the D7 rad3-12 strain failed to remove the induced lesions and could not incise cross-links. The strain D7 rad18-1 was nearly as efficient in the removal of 8-MOP photoadducts after 2 h of post-treatment incubation as the D7 RAD+ wild-type strain. However, as demonstrated by alkaline step-elution and electron microscopic analysis, the first incision step at DNA cross-links was three times more effective in D7 rad18-1 than in D7 RAD+. This is consistent with the hypothesis that the RAD18 gene product is involved in the filling of gaps resulting from persistent non-informational DNA lesions generated by the endonucleolytic processing of DNA cross-links. Absence of this gene product may lead to extensive strand breakage and decreased recognition of such lesions by structural repair systems.
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  • 71
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Ty ; Transcriptional activation ; SPT13/GAL11 ; SPT14
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To investigate the role of the trans-acting transcription factor encoded by the essential SPT14 (SPT=Suppressor of Ty insertion mutations) gene, we have cloned, mapped and sequenced the gene. From the analysis of the effect of spt14 mutations on expression of various genes, we conclude that the SPT14 product has an important role in activation of Ty transcription as well as in the regulation of other genes including HIS4 and several of the a- and α-specific mating type genes. Similarities in the phenotypes of spt14 and spt13 mutants (suppression of Ty insertion mutations but not δ insertion mutations), lead to the suggestion that the SPT14 gene and the previously characterized SPT13/GAL11 gene might encode transcriptional regulators with related functions. Our current findings show that in contrast to SPT13/GAL11, which appears negatively to regulate Ty transcription, SPT14 plays a role in the activation of Ty transcription. Thus, despite the similarities in the suppression phenotype exhibited by spt13 and spt14 mutants, SPT13/GAL11 and SPT14 probably differ in their transcriptional roles.
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  • 72
    ISSN: 1617-4623
    Keywords: DNA bending ; Autonomously replicating sequence ; Saccharomyces cerevisiae ; Basidiomycete ; Linear plasmid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Previous studies have indicated that DNA bending is a general structural feature of sequences (ARSs) from cellular DNAs of yeasts and nuclear and mitochondrial genomic DNAs of other eukaryotes that are capable of autonomous replication in Saccharomyces cerevisiae. Here we showed that bending activity is also tightly associated with S. cerevisiae ARS function of segments cloned from mitochondrial linear DNA plasmids of the basidiomycetes Pleurotus ostreatus and Lentinus edodes. Two plasmids, designated pLPO2-like (9.4 kb), and pLPO3 (6.6 kb) were isolated from a strain of P. ostreatus. A 1029 by fragment with high-level ARS activity was cloned from pLPO3 and it contained one ARS consensus sequence (A/T)TTTAT(A/G)TTT(A/T) indispensable for activity and seven dispersed ARS consensus-like (10/11 match) sequences. A discrete bent DNA region was found to lie around 500 by upstream from the ARS consensus sequence (T-rich strand). Removal of the bent DNA region impaired ARS function. DNA bending was also implicated in the ARS function associated with a 1430 by fragment containing three consecutive ARS consensus sequences which had been cloned from the L. edodes plasmid pLLE1 (11.0 kb): the three consecutive ARSs responsible for high-level ARS function occurred in, and immediately adjacent to, a bent DNA region. A clear difference exists between the two plasmid-derived ARS fragments with respect to the distance between the bent DNA region and the ARS consensus sequence(s).
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    Molecular genetics and genomics 237 (1993), S. 306-310 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Gene replacement ; Donation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We describe here a new method for the introduction of non-selectable alleles into Saccharomyces cerevisiae, gene replacement by donation. This method only requires the availability of an autonomously replicating, selectable plasmid containing the allele to be introduced into yeast. The plasmid is digested at a restriction site (or sites) within this allele, and introduced into yeast by transformation. In the course of double-strand break repair, the entering plasmid donates genetic information to the chromosome, replacing the chromosomal allele in a gene conversion-like event. Gene replacement events are identified by a phenotypic screen of the transformants. When necessary, the transforming plasmid may be subsequently lost by segregation during permissive growth. We have studied several parameters affecting the utility of this protocol as a method of gene replacement. Together with our previous results, the results show gene replacement by donation to be a useful, facile method, yielding gene replacement in up to 1.5% of transformants.
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  • 74
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Formaldehyde hyper-resistance ; Alcohol dehydrogenase ; Glutathione ; Inducibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A 3.7 kb DNA fragment of yeast chromosome IV has been sequenced that contains the SFA gene which, when present on a multi-copy plasmid in Saccharomyces cerevisiae, confers hyper-resistance to formaldehyde. The open reading frame of SFA is 1158 by in size and encodes a polypeptide of 386 amino acids. The predicted protein shows strong homologies to several mammalian alcohol dehydrogenases and contains a sequence characteristic of binding sites for NAD. Overexpression of the SFA gene leads to enhanced consumption of formaldehyde, which is most probably the reason for the observed hyper-resistance phenotype. In sfa:LEU2 disruption mutants, sensitivity to formaldehyde is correlated with reduced degradation of the chemical. The SFA gene shares an 868 by divergent promoter with UGX2 a gene of yet unknown function. Promoter deletion studies with a SFA promoter-lacZ gene fusion construct revealed negative interference on expression of SFA by upstream sequences. The upstream region between positons − 145 and − 172 is totally or partially responsible for control of inducibility of SFA by chemicals such as formaldehyde (FA), ethanol and methyl methanesulphonate. The 41 kDa SFA-encoded protein was purified from a hyper-resistant transformant; it oxidizes long-chain alcohols and, in the presence of glutathione, is able to oxidize FA. SFA is predicted to code for a long-chain alcohol dehydrogenase (glutathione-dependent formaldehyde dehydrogenase) of the yeast S. cerevisiae.
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  • 75
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    Molecular genetics and genomics 238 (1993), S. 315-324 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Nuclear gene ; Mitochondrial enzyme ; Lactate dehydrogenase ; Flavoprotein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Saccharomyces cerevisiae the utilization of lactate occurs via specific oxidation of l- and d-lactate to pyruvate catalysed by l-lactate ferricytochrome c oxidoreductase (L-LCR) (EC 1.1.2.3) encoded by the CYB2 gene, and d-lactate ferricytochrome c oxidoreductase (D-LCR) (EC 1.1.2.4), respectively. We selected several lactate− pyruvate+ mutants in a cyb2 genetic background. Two of them were devoid of D -LCR activity (dld mutants, belonging to the same complementation group). The mutation mapped in the structural gene. This was demonstrated by a gene dosage effect and by the thermosensitivity of the enzyme activity of thermosensitive revertants. The DLD gene was cloned by complementation for growth on d-, l-lactate in the strain WWF18-3D, carrying both a CYB2 disruption and the dld mutation. The minimal complete complementing sequence was localized by subcloning experiments. From the sequence analysis an open reading frame (ORF) was identified that could encode a polypeptide of 576 amino-acids, corresponding to a calculated molecular weight of 64000 Da. The deduced protein sequence showed significant homology with the previously described microsomal flavoprotein l-gulono-γ-lactone oxidase isolated from Rattus norvegicus, which catalyses the terminal step of l-ascorbic acid biosynthesis. These results are discussed together with the role of L-LCR and D-LCR in lactate metabolism of S. cerevisiae.
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  • 76
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; DNA amplification ; Minisatellites ; VNTR ; MS1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Minisatellites comprise arrays of tandemly repeated short DNA sequences which show extensive variation in repeat unit number. The mechanisms that underlie this length variation are not understood. In order to study processes influencing length changes of minisatellites, we integrated the human minisatellite MS1 into a haploid strain of the yeast Saccharomyces cerevisiae. Frequent spontaneous generation of MS1 alleles with new lengths were observed in this yeast strain. Hence it is concluded that recombination between members of a pair of homologous chromosomes is not a prerequisite for the generation of length changes in MS1 in yeast.
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  • 77
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Splicing ; prp mutants ; Linker insertion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the yeast Saccharomyces cerevisiae, some thermosensitive (ts) mutants have been shown to be impaired in pre-mRNA splicing (prp mutants). From a yeast genomic library, we have isolated plasmids that complement prp6 or prp9 is mutations. These plasmids also complement the is growth defect of additional independent mutants identified as new prp6 and prp9 is alleles, indicating that the cloned DNAs encode PRP6 and PRP9 genes, respectively. Here, we describe the restriction maps of these loci which are localized on chromosome II and IV, respectively. The limits of open reading frames (ORFs) within the cloned inserts have been determined using a linker insertion strategy combined with the is complementation assay. Double-strand DNA sequencing was also performed directly on the yeast expression vector from the inserted linkers. Gene disruption experiments demonstrate that both genes are essential for viability.
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  • 78
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; TRPI promoter ; Upstream activating sequences ; PGK
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    Topics: Biology
    Notes: Summary The interactions between different upstream activator sequences (UAS) and the downstream transcriptional elements of the TRP1 promoter were studied. We have inserted the UAS from the PGK gene into a series of TRP1 promoter deletions such that the PGK UAS is positioned at various distances upstream from or replaces the TRP1 UAS (UAST1). We show that activation of the TRP1 transcription unit I by the PGK UAS shows a marked position dependence, which is solely a function of the position of the PGK UAS relative to sequences involved in the determination of the RNA initiation sites in the TRP1 promoter. No cooperative activation is seen when both UASs are present in the promoter; the PGK UAS is dominant and is not repressed by the TRPI negative element. In addition, we show that the PGK and TRP1 UASs interact differently with TATA sequence at the TRP1 RNA initiation site. Our results suggest that these UASs are functionally distinct because they use different mechanisms for activating heterologous promoters.
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  • 79
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    Molecular genetics and genomics 225 (1991), S. 340-341 
    ISSN: 1617-4623
    Keywords: Intron ; Group I ; DNA endonuclease ; Mitochondria ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two group I intron-encoded proteins from the yeast mitochondrial genome have already been shown to have a specific DNA endonuclease activity. This activity mediates intron insertion by cleaving the DNA sequence corresponding to the splice junction of an intronless strain. We have discovered in mitochondrial extracts from the yeast strain 777-3A a new DNA endonuclease activity which cleaves the fused exon A3-exon A4 junction sequence of the COXI gene.
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  • 80
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Centromere and promoter factor ; Chromatin ; SPT ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Saccharomyces cerevisiae, the CPF1 gene encodes a ccntromere binding protein that also plays a role in transcription; cpf1 strains are methionine auxotrophs. In this paper we describe four strains that are methionine prototrophs despite containing a defective CPF1 gene. These strains, which contain mutations at either the SPT21, RPD1 (SINS), RPD3 or CCR4 loci, have defective centromere function and a chromatin structure around the CDEI elements in the MET25 promoter characteristic of strains lacking CPF1. This indicates that the roles of CPF1 in transcription, centromere function and chromatin modulation around CDEI sites are different. We propose that CPF1 functions to overcome the repressing action, mediated via inactive chromatin, of proteins such as SPT21 or RPDI (SIN3) on gene expression. The absence of proteins such as SPT21 or RPD1 (SIN3) relieves this respression and explains how methionine prototrophy is restored in the absence of CPF1.
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  • 81
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    Molecular genetics and genomics 240 (1993), S. 414-418 
    ISSN: 1617-4623
    Keywords: Cruciform DNA ; Endonuclease ; Mitochondria ; Saccharomyces cerevisiae
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    Topics: Biology
    Notes: Abstract We have found a cruciform cutting endonuclease in the yeast, Saccharomyces cerevisiae, which localizes to the mitochondria. This activity apparently is associated with the mitochondrial inner membrane since the activity is not released into solution by osmolysis, in contrast to the matrix enzyme, isocitrate dehydrogenase. The cruciform cutting activity appears to be encoded by CCE1. This gene has been shown to encode one of the major cruciform cutting endonucleases present in a yeast cell. In ccel strains, which lack CCE1 endonuclease activity, the mitochondrial cruciform cutting endonucleolytic activity is also absent. Since CCE1 is allelic to MGT1, a gene required for the highly biased transmission of petite mitochondrial DNA in crosses between ϱ+ and hypersuppressive ϱ− cells, it seems likely that the CCE1 endonuclease functions within mitochondria.
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  • 82
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    Molecular genetics and genomics 241 (1993), S. 213-224 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Mitochondria ; Transcriptional regulation ; Protein phosphorylation ; Stringent response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using various mutant strains and nutritional manipulations, we investigated a potential role for cyclic AMP (cAMP) in the regulation of mitochondrial (mt) gene expression in the yeast Saccharomyces cerevisiae. In RAS mutants known to have either abnormally low or high cellular levels of this nucleotide, we show that both mt transcription rate and overall mt transcript levels vary directly with cellular cAMP levels. We further show that nutritional downshift of actively growing cells causes a severe, rapid fall in cAMP levels, and that this fall is concomitant with the stringent mt transcriptional curtailment that we and others have previously shown to follow this nutritional manipulation. In in vitro mt transcription assays using intact organelles from downshifted and actively growing cells, stringently curtailed mt gene expression can be restored to 75% of control levels by addition of cAMP to the assay mix. Consistent with these observations a RAS2 vall9mutant strain, which cannot adjust cAMP levels in response to external stimuli, shows no mt stringent response following nutritional downshift. We also demonstrate a significant but transient increase in both mt transcript levels and mt transcription rate following shift of actively respiring wild-type cells to glucose-based medium, a manipulation known to cause a short-lived pulse of cAMP in yeast; similar manipulation of the RAS2 vall9mutant strain generates no such response. Taken together all these observations indicate that cellular cAMP levels are involved in the regulation of mt transcription in yeast. Moreover, the lack of a mt stringent transcriptional response following downshift in a strain in which the BCY1 gene had been insertionally inactivated suggests that cAMP may influence mt transcription via a mt cAMP-dependent protein kinase. These results link mt gene expression with mechanisms governing growth control and nutrient adaptation in yeast, and they provide a means by which nit gene expression might be coordinated with that of related nuclear genes.
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  • 83
    ISSN: 1617-4623
    Keywords: Mating pheromone ; Saccharomyces cerevisiae ; Signal transduction ; STE5 ; Ste20 protein kinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The β and γ subunits of the mating response G-protein in the yeast Saccharomyces cerevisiae have been shown to transmit the mating pheromone signal to downstream components of the pheromone response pathway. A protein kinase homologue encoded by the STE20 gene has recently been identified as a potential G βγ , target. We have searched multicopy plasmid genomic DNA libraries for high gene dosage suppressors of the signal transduction defect of ste20 mutant cells. This screen identified the STE5 gene encoding an essential component of the pheromone signal transduction pathway. We provide genetic evidence for a functional interrelationship between the STE5 gene product and the Ste20 protein kinase. We have sequenced the STE5 gene, which encodes a predicted protein of 917 amino acids and is specifically transcribed in haploid cells. Transcription is slightly induced by treatment of cells with pheromone. Ste5 has homology with Fart, a yeast protein required for efficient mating and the pheromone-inducible inhibition of a G1 cyclin, Cln2. A STE5 multicopy plasmid is able to suppress the signal transduction defect of farl null mutant cells suggesting that Ste5, at elevated levels, is able functionally to replace Fart. The genetically predicted point of function of Ste5 within the pheromone signalling pathway suggests that Stc5 is involved in the regulation of a Gβγ-activated protein kinase cascade which links a G-protein coupled receptor to yeast homologues of mitogen-activated protein kinases.
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  • 84
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    Molecular genetics and genomics 241 (1993), S. 280-286 
    ISSN: 1617-4623
    Keywords: Yeast RAS ; RAS-CAMP pathway ; Saccharomyces cerevisiae
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    Topics: Biology
    Notes: Abstract A mutant allele of RAS1 that dominantly interferes with the wild-type Ras function in the yeast Saccharomyces cerevisiae was discovered during screening of mutants that suppress an ira2 disruption mutation. A single amino acid substitution, serine for glycine at position 22, was found to cause the mutant phenotype. The inhibitory effect of the RAS1 Ser22 gene could be overcome either by overexpression of CDC25 or by the ira2 disruption mutation. These results suggest that the RAS1Ser22 gene product interferes with the normal interaction of Ras with Cdc25 by forming a dead-end complex between Ras1Ser22 and Cdc25 proteins.
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  • 85
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; RNA polymerase II ; Cyclins ; Transcription ; Cell cycle
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    Topics: Biology
    Notes: Abstract Saccharomyces cerevisiae cells harboring the temperature-sensitive mutation rpo21-4, in the gene encoding the largest subunit of RNA polymerase II, were shown to be partially impaired for cell-cycle progress at a permissive temperature, and to become permanently blocked at the cell-cycle regulatory step, START, at a restrictive temperature. The rpo21-4 mutation was lethal in combination with cdc28 mutations in the p34 protein kinase gene required for START. Transcripts of the CLN1 and CLN2 genes, encoding G1-cyclin proteins that, along with p34, are necessary for START, were decreased in abundance by the rpo21-4 mutation at a restrictive temperature. Increased G1-cyclin production, by expression of the CLN1 or CLN2 genes from a heterologous GAL promoter, overcame the rpo21-4 — mediated START inhibition, but such mutant cells nevertheless remained unable to proliferate at a restrictive temperature. These findings reveal that START can be particularly sensitive to an impaired RNA polymerase II function, presumably through effects on G1-cyclin expression.
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  • 86
    ISSN: 1617-4623
    Keywords: Transcriptional activators ; O2 gene ; Zea mays ; bZIP proteins ; Saccharomyces cerevisiae
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    Topics: Biology
    Notes: Abstract The aim of this research was to determine whether the structural homology between the O2 gene, a maize transcriptional activator, and the GCN4 gene, a yeast transcriptional factor, is reflected at the level of function. The O2 cDNA was cloned in the yeast expression vector pEMBLyex4 under the control of a hybrid, inducible promoter, and used to transform the yeast Saccharomyces cerevisiae. Transformed yeast cells produced O2 mRNA and a polypeptide immunoreactive with anti-O2 antibodies during growth in galactose. The heterologous protein was correctly translocated into the yeast nuclei, as demonstrated by immunofluorescence, indicating that the nuclear targeting sequences of maize are recognized by yeast cells. Further experiments demonstrated the ability of O2 to rescue a gcn4 mutant grown in the presence of aminotriazole, an inhibitor of the HIS3 gene product, suggesting that O2 activates the HIS3 gene, gene normally under control of GCN4. It was shown that the O2 protein is able to trans-activate the HIS4 promoter in yeast cells and binds to it in vitro. The sequence protected by O2, TGACTC, is also the binding site for GCN4. Finally, the expression of O2 protein in yeast did not produce alterations during batch growth at 30° C, while transformants expressing O2 protein showed a conditionally lethal phenotype when grown in galactose at 36° C; this phenotype mimics the behaviour of gcd mutants. The results support the idea that basic mechanisms of transcription control have been highly conserved in eukaryotes.
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  • 87
    ISSN: 1617-4623
    Keywords: RNase H ; Salmonella typhimurium ; Saccharomyces cerevisiae
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    Topics: Biology
    Notes: Summary We have cloned genes encoding RNase H from Escherichia coli rnh mutants, Salmonella typhimurium and Saccharomyces cerevisiae. Selection was accomplished by suppression of the temperature-sensitive growth phenotype of Escherichia coli strains containing the rnh-339::cat and either recB270 (Ts) or recC271 (Ts) mutations. RNases H from E. coli and S. typhimurium contained 155 amino acid residues and differed at only 11 positions. The S. cerevisiae and E. coli RNases H were about 30% homologous. A comparison of the amino acid sequences of several RNases H from cellular and retroviral sources revealed some strongly conserved regions as well as variable regions; the carboxyl-terminus was particularly variable. The overlapping, divergent promoter gene organization found in E. coli was observed to be present in S. typhimurium.
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  • 88
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    Molecular genetics and genomics 227 (1991), S. 452-457 
    ISSN: 1617-4623
    Keywords: CDC7 ; Saccharomyces cerevisiae ; Protein kinase ; Cell cycle ; DNA synthesis
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    Topics: Biology
    Notes: Summary The product of the CDC7 gene of Saccharomyces cerevisiae has multiple cellular functions, being needed for the initiation of DNA synthesis during mitosis as well as for synaptonemal complex formation and commitment to recombination during meiosis. The CDC7 protein has protein kinase activity and contains the conserved residues characteristic of the protein kinase catalytic domain. To determine which of the cellular functions of CDC7 require this protein kinase activity, we have mutated some of the conserved residues within the CDC7 catalytic domain and have examined the ability of the mutant proteins to support mitosis and meiosis. The results indicate that the protein kinase activity of the CDC7 gene product is essential for its function in both mitosis and meiosis and that this activity is potentially regulated by phosphorylation of the CDC7 protein.
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  • 89
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    Molecular genetics and genomics 236 (1993), S. 443-447 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Protein kinases ; Protein Kinase C ; Growth control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Probes derived from cDNAs encoding isozymes of rat protein kinase C (PKC) were used to screen the genome of the budding yeast Saccharomyces cerevisiae. We reported previously the isolation of the yeast PKC1 gene, a homolog of the α, β, and γ subspecies of mammalian PKC. Here we report the isolation and genetic characterization of a pair of previously described genes (YPK1 and YPK2) which are predicted to encode protein kinases that share 90% amino acid identity with each other and 44–46% identity with various isozymes of PKC throughout their putative catalytic domains. Deletion of YPK2 resulted in no apparent phenotypic defect, but loss of YPK1 resulted in slow growth. Cells deleted for both YPK1 and YPK2 were defective in vegetative growth, indicating that the protein kinases predicted to be encoded by these genes are functionally overlapping and play an essential role in the proliferation of yeast cells. The YPK1 gene was mapped to the left arm of chromosome XI and YPK2 was mapped to the right arm of chromosome XIII.
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  • 90
    ISSN: 1573-6881
    Keywords: Rieske iron-sulfur protein, RIP1 ; Saccharomyces cerevisiae ; mitochondria ; bc 1 complex ; QCR9 ; iron-sulfur cluster, mitochondrial targeting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The iron-sulfur protein of the cytochromebc 1 complex oxidizes ubiquinol at center P in the protonmotive Q cycle mechanism, transferring one electron to cytochromec 1 and generating a low-potential ubisemiquinone anion which reduces the low-potential cytochromeb-566 heme group. In order to catalyze this divergent transfer of two reducing equivalents from ubiquinol, the iron-sulfur protein must be structurally integrated into the cytochromebc 1 complex in a manner which facilitates electron transfer from the iron-sulfur cluster to cytochromec 1 and generates a strongly reducing ubisemiquinone anion radical which is proximal to theb-566 heme group. This radical must also be sequestered from spurious reactivities with oxygen and other high-potential oxidants. Experimental approaches are described which are aimed at understanding how the iron-sulfur protein is inserted into center P, and how the iron-sulfur cluster is inserted into the apoprotein.
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  • 91
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    World journal of microbiology and biotechnology 9 (1993), S. 583-586 
    ISSN: 1573-0972
    Keywords: Cell-free extracts ; plasmids ; recombination ; Saccharomyces cerevisiae ; topo-isomerase mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cell-free extracts of the yeast Saccharomyces cerevisiae can be used to catalyse the recombination of bacterial plasmids in vitro. Recombination between homologous plasmids containing different mutations in the gene encoding tetracycline resistance is detectable by the appearance of tetracycline-resistance following transformation of the recombinant plasmid DNA into Escherichia coli DH5. This in vitro recombination system was used to determine the involvement of eukaryotic topo-isomerases in genetic recombination. Cell-free extracts prepared from a temperature-sensitive topo-isomerase II mutant (top2-1) of S. cerevisiae yielded tetracycline-resistant recombinants, when the recombination assays were performed at both a non-restrictive temperature (30°C) and the restrictive temperature (37°C). This result was obtained whether or not ATP was present in the recombination buffer. Extracts from a non-conditional topo-isomerase I mutant (top1-1) of S. cerevisiae yielded tetracycline-resistant recombinants, as did a temperature-sensitive double mutant (top2-1/top1-8) at the restrictive temperature. The results of this study indicate that neither topo-isomerase I nor topo-isomerase II was involved in the recombinational activity examined.
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  • 92
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    World journal of microbiology and biotechnology 9 (1993), S. 662-663 
    ISSN: 1573-0972
    Keywords: Biosynthesis ; invertase ; molasses ; Saccharomyces cerevisiae ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Biosynthesis of invertase by Saccharomyces cerevisiae 01K32 was inversely proportional to the concentration of sugarcane blackstrap molasses included in the medium. In a fermenter, an intracellular invertase activity of 440 U/g dry cells was obtained.
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  • 93
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    Antonie van Leeuwenhoek 59 (1991), S. 269-283 
    ISSN: 1572-9699
    Keywords: growth physiology ; plasmid stability ; recombinant cell culture ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Despite the fact that plasmid stability in the yeastSaccharomyces cerevisiae is influenced by both genetical and physiological parameters most attention has been focussed on the former. Physiological factors affecting the stability of plasmids have been poorly characterized despite the need for such information in order to optimize the use ofS. cerevisiae as a host for recombinant protein production processes. The physiology of wild typeS. cerevisiae differs considerably when grown using different cultivation techniques. A limited amount of phenomenological data has been reported concerning plasmid instability effects under these different conditions and in this article these have been collected together with the intention of providing an overview to instability effects and to try and propose reasons as to how the physiological response to different growth conditions can be manifested as stability/instability effects.
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  • 94
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    Antonie van Leeuwenhoek 63 (1993), S. 343-352 
    ISSN: 1572-9699
    Keywords: alcoholic fermentation ; chemostat culture ; Crabtree effect ; respiration ; Saccharomyces cerevisiae ; yeasts
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    Topics: Biology
    Notes: Abstract An overview is presented of the steady- and transient state kinetics of growth and formation of metabolic byproducts in yeasts.Saccharomyces cerevisiae is strongly inclined to perform alcoholic fermentation. Even under fully aerobic conditions, ethanol is produced by this yeast when sugars are present in excess. This so-called ‘Crabtree effect’ probably results from a multiplicity of factors, including the mode of sugar transport and the regulation of enzyme activities involved in respiration and alcoholic fermentation. The Crabtree effect inS. cerevisiae is not caused by an intrinsic inability to adjust its respiratory activity to high glycolytic fluxes. Under certain cultivation conditions, for example during growth in the presence of weak organic acids, very high respiration rates can be achieved by this yeast.S. cerevisiae is an exceptional yeast since, in contrast to most other species that are able to perform alcoholic fermentation, it can grow under strictly anaerobic conditions. ‘Non-Saccharomyces’ yeasts require a growth-limiting supply of oxygen (i.e. oxygen-limited growth conditions) to trigger alcoholic fermentation. However, complete absence of oxygen results in cessation of growth and therefore, ultimately, of alcoholic fermentation. Since it is very difficult to reproducibly achieve the right oxygen dosage in large-scale fermentations, non-Saccharomyces yeasts are therefore not suitable for large-scale alcoholic fermentation of sugar-containing waste streams. In these yeasts, alcoholic fermentation is also dependent on the type of sugar. For example, the facultatively fermentative yeastCandida utilis does not ferment maltose, not even under oxygen-limited growth conditions, although this disaccharide supports rapid oxidative growth.
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  • 95
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    The European physical journal 26 (1993), S. 175-177 
    ISSN: 1434-6079
    Keywords: 36.40 ; 67.90+Z ; 71.90+Q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Excitation and decay processes of helium clusters are investigated with fluorescence methods. The results differ remarkably from that obtained for the heavier rare gas clusters. They are discussed in view of the unusual structural and electronic properties of helium.
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  • 96
    ISSN: 1434-6079
    Keywords: 76.60 ; 03.65.F ; 36.40
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    Topics: Physics
    Notes: Abstract For both highern andI i ≧1 spin clusters, combinatorics provides powerful arguments with which to investigate the substructural forms of cluster spin algebras; this is especially so for SO(3) ×l n symmetries for 12≦n≦60 wherex (.) [λ] character tabulations become extensive. Bijective enumerative mappings over the combinatorialp-tuples (number partitions) afford insight into the general functionf(p,n) as well as into {|IM(I 1−I n [λ]〉} M -structure of spin algebras, even where the full details of the explicitx () [λ] (l n ) characters are not readily available. Both simply-reducible and higher aspects ofl n -inner tensor product (ITP) algebras are derived from dimensionality considerations, as part of combinatorial hooklength formalisms for $$\chi _{(1^n )}^{[\lambda ]} $$ . TheI i ≦3/2 forms of [A] n clusters forn≦20, (forp≦3, 4) of multiple-quantum NMR (MQ-NMR) are considered here as part of current interest in giant cage-clusters. In addition, the SU2 substructural hierarchy over Liouville space is derived for [A]20(l n ) (I i =1/2) spin cluster of the cage-cluster molecule dodecahedrane; aspects ofI i =1 spin cluster over {|IM (...)〉} space are derived as high temperature model of the exo-cage of [H2O]+ @[H2O]20 cluster ion; 20-fold higher-I i lusters provide models for M @M20 metal-clusters and further applications ofl 20-number partitions.
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    The European physical journal 26 (1993), S. 255-257 
    ISSN: 1434-6079
    Keywords: 36.40
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    Topics: Physics
    Notes: Abstract Molecular dynamics is used to study the melting and structural transitions of small copper clusters. The melting temperature is found to be proportional to the average coordination number. Small icosahedral clusters melt at slightly higher temperatures than the cubic structures. Small cuboctahedral clusters are not stable but transform via a nondiffusive transition to icosahedral structure.
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    The European physical journal 26 (1993), S. 261-263 
    ISSN: 1434-6079
    Keywords: 36.40
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    Topics: Physics
    Notes: Abstract We apply the nuclear shell model to jellium clusters of up to twenty-one Na atoms. Binding energies, ionization potentials, and photoabsorption cross sections are calculated and compared with mean-field results.
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    The European physical journal 26 (1993), S. 322-324 
    ISSN: 1434-6079
    Keywords: 36.40 ; 33.80.E
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    Topics: Physics
    Notes: Abstract The ionization potentials of AlnCom clusters (n〉m) have been bracketed using laser photoionization mass spectrometry. We find the electronic shell structure manifested in the ionization potentials of Aln for n≥7 is observed also for AlnCo and AlnCo2, and is consistent with cobalt contributing one electron to the conduction band of the cluster. However, with increasing number of cobalt atoms, this simple picture breaks down; all vestiges of aluminum cluster electronic shell structure are absent for m≥4.
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  • 100
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    The European physical journal 26 (1993), S. 364-366 
    ISSN: 1434-6079
    Keywords: 36.40 ; 64.60.Qb ; 64.70.Kb ; 82.20.Wt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Simulations of clusters containing 100 to 250 molecules of TeF6 successfully reproduce the crystalline packing arrangements observed in electron diffraction investigations of large molecular clusters (∼ 104 molecules) of the same material. More remarkably, when the clusters are cooled step by step in MD computations at a rate of ca. 1011 K/s they spontaneously undergo the same bcc to monoclinic phase transition that has been observed experimentally in supersonic flow, despite the million-fold difference in the timescales involved. The existence of such a correspondence over so many orders of magnitude, in itself, imposes severe constraints on what type of molecular mechanism can underlie the transformation. Even more revealing evidence about the molecular behavior associated with the phase change is provided by the simulations. They show the formation of the actual transition complexes along the transition pathway, namely, the critical nuclei of the new phase. These nuclei, which are made up of approximately 20 molecules, can be recognized in the midst of the surrounding matter. Techniques based on molecular orientations, involving Pawley-Fuchs projections and orientational angular distribution functions, make it possible to estimate the size of critical nuclei. One noteworthy result established in the simulations is that the solid-state transition temperature from bcc to monoclinic depends upon particle size in the same manner as does the freezing point.
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