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  • Articles  (8)
  • Springer  (6)
  • Cambridge University Press  (2)
  • ZBW - Deutsche Zentralbibliothek für Wirtschaftswissenschaften, Leibniz-Informationszentrum Wirtschaft Kiel, Hamburg
  • Biology  (8)
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  • Articles  (8)
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  • 1
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Cytochrome c 1 ; Promoter dissection ; HAP1, HAP2 transcription factors ; Centromere and promoter-binding factor (CPF1)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nuclear gene for cytochrome c 1 in Saccharomyces cerevisiae (CYT1) was localized on chromosome XV. Its upstream region was identified by functional complementation. Fusion to the lacZ reporter gene on a CEN plasmid allowed study of the effect of carbon sources and of specific deletion mutations on expression of the gene in yeast transformants. Detailed promoter analysis combined with expression studies in recipient strains defective in regulatory genes identified cis-acting sites and transcription factors involved in the regulated expression of the cytochrome c 1 gene. These analyses showed that, in the presence of glucose, transcription of CYT1 is positively controlled by oxygen, presumably through the haem signal, and mediated by the HAP1-encoded transactivator. It is additionally regulated by the HAP2/3/4 complex which mediates gene activation mainly under glucose-free conditions. Basal transcription is, in part, effected by CPF1, a centromere and promoter-binding factor.
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  • 2
    ISSN: 1617-4623
    Keywords: Chloramphenicol resistance ; frameshifting Mitochondria ; 21S rRNA ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A mutation shown to cause resistance to chloramphenicol inSaccharomyces cerevisiae was mapped to the central loop in domain V of the yeast mitochondrial 21S rRNA. The mutant 21S rRNA has a base pair exchange from U2677 (corresponding to U2504 inEscherichia coli) to C2677, which significantly reduces rightward frameshifting at a UU UUU UCC A site in a + 1 U mutant. There is evidence to suggest that this reduction also applies to leftward frameshifting at the same site in a − 1 U mutant. The mutation did not increase the rate of misreading of a number of mitochondrial missense, nonsense or frameshift (of both signs) mutations, and did not adversely affect the synthesis of wild-type mitochondrial gene products. It is suggested here that ribosomes bearing either the C2677 mutation or its wild-type allele may behave identically during normal decoding and only differ at sites where a ribosomal stall, by permitting non-standard decoding, differentially affects the normal interaction of tRNAs with the chloramphenicol resistant domain V. Chloramphenicol-resistant mutations mapping at two other sites in domain V are described. These mutations had no effect on frameshifting.
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  • 3
    ISSN: 1432-0983
    Keywords: Genetic mapping ; Mutant polypeptides ; Direction of translation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Genetic and biochemical studies have been performed with 110 mutants which are defective in cytochrome a·a3 and map in the regions on mit DNA previously designated OXI1 and OXI2. With 88 mutations allocated to OXI1 fine structure mapping was achieved by the analysis of rho − deletions. The order of six groups of mutational sites (A 1, A2, B 1, B2, C 1, C2) thus determined was confirmed by oxi i x oxi j recombination analysis. Analysis of mitochondrially translated polypeptides of oxil mutants by SDS-polyacrylamide electrophoresis reveals three classes of mutant patterns: i) similar to wild-tpye (19 mutants); ii) lacking SU II of cytochrome c oxidase (53 mutants); iii) lacking this subunit and exhibiting a single new polypeptide of lower Mr (16 mutants). Mutations of each of these classes are scattered over the OXI1 region without any detectable clustering; this is consistent with the assumption that all oxil mutations studied are within the same gene. New polypeptides observed in oxil mutants of class iii) vary in Mr in the range from 10,500 to 33,000. Those of Mr 17,000 to 33,000 are shown to be antigenically related to subunit II of cytochrome c oxidase. Colinearity is established between the series of new polypeptides of Mr values increasing from 10,500 to 31,500 and the order of the respective mutational sites on the map, e.g. mutations mapping in A 1 generate the smallest and mutations mapping in C2 the largest mutant fragments. From these data we conclude that i) all mutations allocated to the OXI1 region are in the same gene; ii) this gene codes for subunit II of cytochrome c oxidase; iii) the direction of translation is from CAP to 0X12. Out of 19 mutants allocated to OXI2 three exhibit a new polypeptide; these and all the other oxi2 mutants lack subunit III of cytochrome oxidase. This result provides preliminary evidence that the OXI2 region harbours the structural gene for this subunit III.
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  • 4
    ISSN: 1432-0983
    Keywords: Intervening sequence mutations ; RNA blotting ; Transcript hybridization ; RNA processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Electrophoretic separation of mitochondrial RNA followed by hybridization with restriction fragments of mtDNA has been used to identify transcripts of the split gen COB which codes for apocytochrome b. In wild type a major transcript of 18S is detected besides a 10S RNA and a series of transcripts with electrophoretic mobilities higher than 18S. Mutations in coding sequences do not significantly alter this transcript pattern. In contrast, mutations in intervening sequences give rise to different patterns: The 18S RNA, the putative messenger for apocytochrome b, is lacking; depending on the intervening sequence affected by mutation, one or the other of the larger transcripts (23S, 24S, 32S, 34S) is accumulated instead. In most mutants a 10S RNA species is present; it has not been detected, however, in case of a small cluster of mutations which lead to the accumulation of the largest transcript (34S) observed, which most likely contains all coding and intervening sequences of the split gene COB. These results suggest a pathway of splicing.
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  • 5
    ISSN: 1432-2048
    Keywords: Ectomycorrhiza ; Elicitor inactivation ; Elicitor-induced reaction ; Hebeloma — Picea cells ; Signal transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Elicitors released from hyphae or cell walls of the ectomycorrhizal fungus Hebeloma crustuliniforme (Bull. ex Fries.) Quél. induced in suspension-cultured cells of Picea abies (L.) Karst. a set of fast reactions: (i) an immediate efflux of Cl− into the medium, followed by a K+ efflux; (ii) an influx of Ca2+ (measured as accumulation of 45Ca2+ in the cells); (iii) a phosphorylation of a 63-kDa protein and dephosphorylation of a 65-kDa protein (detectable by 4 min after elicitor application); (iv) an alkalinization of the medium, and (v) a transient synthesis of H2O2. The removal of extracellular Ca2+ by EGTA delayed the elicitor-induced alkalinization. A further reduction of this response could be achieved by TMB-8 an inhibitor of Ca2+ release from intracellular stores. Moreover, the inhibition of protein kinase activity by staurosporine prevented the extracellular alkalinization completely. However, the effectiveness of the elicitors in inducing the extracellular alkalinization was strongly impaired by constitutively secreted enzymes of spruce cells which cleaved the elicitors to inactive fragments. It is suggested that in ectomycorrhizae the efficacy of elicitors released from fungal cell walls is controlled by apoplastic enzymes of the host; the plant itself is able to reduce the activity of fungal elicitors on their way through the plant cell wall. But those elicitors which finally reach the plasma membrane of host cells induce reactions that are similar to the early defense reactions in plant-pathogen interactions.
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  • 6
    ISSN: 1432-0983
    Keywords: Cytochrome c 1 ; Cytochrome c 1 heme lyase ; GRF2p ; Glucose repression ; HAPp ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this paper we examine the expression of the Saccharomyces cerevisiae CYT2 gene, which encodes cytochrome c 1 heme lyase. This enzyme is required for covalent attachment of heme to apocytochrome c 1, a subunit of the mitochondrial respiratory chain. Transcription of the 1-kb CYT2 mRNA initiates at four prominent sites at a distance of 52–225 bp in front of the AUG start codon. The level of CYT2 mRNA is not influenced by the presence or absence of oxygen or of heme, but it is subject to carbonsource control. The concentration of the CYT2 mRNA is significantly reduced in glucose-grown cells as compared to cells grown under non-repressing conditions. Neither the HAPp activator proteins nor MIG1p, a repressor protein involved in glucose repression, seem to mediate this effect.
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  • 7
    Publication Date: 2015-01-29
    Description: The development of coastal polynyas, areas of enhanced heat flux and sea ice production strongly depend on atmospheric conditions. In Antarctica, measurements are scarce and models are essential for the investigation of polynyas. A robust quantification of polynya exchange processes in simulations relies on a realistic representation of atmospheric conditions in the forcing dataset. The sensitivity of simulated coastal polynyas in the south-western Weddell Sea to the atmospheric forcing is investigated with the Finite-Element Sea ice-Ocean Model (FESOM) using daily NCEP/NCAR reanalysis data (NCEP), 6 hourly Global Model Europe (GME) data and two different hourly datasets from the high-resolution Consortium for Small-Scale Modelling (COSMO) model. Results are compared for April to August in 2007–09. The two coarse-scale datasets often produce the extremes of the data range, while the finer-scale forcings yield results closer to the median. The GME experiment features the strongest winds and, therefore, the greatest polynya activity, especially over the eastern continental shelf. This results in higher volume and export of High Salinity Shelf Water than in the NCEP and COSMO runs. The largest discrepancies between simulations occur for 2008, probably due to differing representations of the ENSO pattern at high southern latitudes. The results suggest that the large-scale wind field is of primary importance for polynya development.
    Print ISSN: 0954-1020
    Electronic ISSN: 1365-2079
    Topics: Biology , Geography , Geosciences
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  • 8
    Publication Date: 2013-11-26
    Description: Mesoscale model simulations were conducted for the Weddell Sea region for the autumn and winter periods of 2008 using a high-resolution, limited-area, non-hydrostatic atmospheric model. A sea ice–ocean model was run with enhanced horizontal resolution and high-resolution forcing data of the atmospheric model. Daily passive thermal and microwave satellite data was used to derive the polynya area in the Weddell Sea region. The focus of the study is on the formation of polynyas in the coastal region of Coats Land, which is strongly affected by katabatic flows. The polynya areas deduced from two independent remote sensing methods and data sources show good agreement, while the results of the sea ice simulation show some weaknesses. Linkages between the pressure gradient force composed of a katabatic and a synoptic component, offshore wind regimes and polynya area are identified. It is shown that the downslope surface offshore wind component of Coats Land is the main forcing factor for polynya dynamics, which is mainly steered by the offshore pressure gradient force, where the katabatic force is the dominant term. We find that the synoptic pressure gradient is opposed to the katabatic force during major katabatic wind events.
    Print ISSN: 0954-1020
    Electronic ISSN: 1365-2079
    Topics: Biology , Geography , Geosciences
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