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  • 1
    Electronic Resource
    Electronic Resource
    Tonoplast intrinsic proteins from cauliflower (Brassica oleracea L. var. botrytis): immunological analysis, cDNA cloning and evidence for expression in meristematic tissues (1998)
    Springer
    Planta 204 (1998), S. 335-344 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Aquaporin (γ-TIP) ; Brassica ; Gene expression ; Meristematic cell ; Tonoplast intrinsic protein ; Vacuole (membrane)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The vacuolar membrane (tonoplast) of plant cells contains aquaporins, protein channels that facilitate the selective transport of water. These tonoplast intrinsic proteins (TIPs) of 23–29 kDa belong to the ancient major intrinsic protein (MIP) family. A monospecific polyclonal antiserum directed against a 26 kDa intrinsic protein from the tonoplast of meristematic cells from cauliflower (Brassica oleracea L. var. botrytis) was used to screen a cDNA library. Two distinct cDNAs have been isolated. Both clones, c26-1 and c26-2, encode closely related TIPs. The c26-1 insert, consisting of 933 bp upstream of the poly(A) tail, is a full-length cDNA with an open reading frame encoding a protein of 251 amino acids with a calculated Mr of 25 500. The c26-2 insert is a 5′ truncated cDNA. The two cDNAs share 90.5% sequence identity within their overlapping coding regions but only 35% sequence identity in the 3′␣untranslated regions, indicating that highly related TIP-encoding genes are expressed in meristematic cells. Although TIPs have previously been found in a variety of cell types, they have not been found in meristems. The derived amino acid sequences (BobTIP26-1 and BobTIP26-2, respectively) closely resemble the aquaporin γ-TIP from Arabidopsis thaliana. Northern blot analysis and in situ hybridization show that BobTIP26 mRNAs preferentially accumulate in highly meristematic cells, mostly before and during cell enlargement, and in the living cells of the xylem. This differential pattern of expression is also found by immunodetection of BobTIP26 polypeptides. The gene expression patterns are discussed with respect to the probable function of the gene products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050264
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  • 2
    Electronic Resource
    Electronic Resource
    Desiccation and osmotic stress increase the abundance of mRNA of the tonoplast aquaporin BobTIP26-1 in cauliflower cells (1999)
    Springer
    Planta 209 (1999), S. 77-86 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Aquaporin ; Brassica (cauliflower) ; Gene regulation ; Tonoplast ; Vacuole ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Changes in vacuolar structure and the expression at the RNA level of a tonoplast aquaporin (BobTIP26-1) were examined in cauliflower (Brassicaoleracea L. var. botrytis) under water-stress conditions. Gradual drying out of slices of cauliflower floret tissue caused its collapse, with a shrinkage in tissue and cell volumes and an apparent vesiculation of the central vacuole, whereas osmotic stress resulted in plasmolysis with a collapse of the cytoplasm and the central vacuole within. Osmotic stress caused a rapid and substantial increase in BobTIP26 mRNA in slices of floret tissue. Exposure of tissue slices to a regime of desiccation showed a slower but equally large rise in BobTIP26 mRNA followed by a rapid decline upon rehydration. In situ hybridization showed that BobTIP26-2 mRNA is expressed most highly in meristematic and expanding cells of the cauliflower florets and that desiccation strongly increased the expression in those cells and in differentiated cells near the xylem vessels. These data indicate that under water-deficit conditions, expression of the tonoplast aquaporin gene in cauliflower is subject to a precise regulation that can be correlated with important cytological changes in the cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050608
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  • 3
    Electronic Resource
    Electronic Resource
    Evolutionary biology Oxygen at life's boundaries (2007)
    [s.l.] : Nature Publishing Group
    Nature 445 (2007), S. 35-36 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] For many microorganisms, one cell is adequate; for some plants and animals, billions are scarcely enough. But whatever the number, the cell is the fundamental unit of living matter, and is invariably delineated by a membrane — the plasma membrane — that is a selective barrier separating ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature05521
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  • 4
    Electronic Resource
    Electronic Resource
    Structure of the HOM2 gene of Saccharomyces cerevisiae and regulation of its expression (1989)
    Springer
    Molecular genetics and genomics 217 (1989), S. 149-154 
    Details
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; HOM2 gene ; Aspartic semi-aldehyde ; General control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Saccharomyces cerevisiae the HOM2 gene encodes aspartic semi-aldehyde dehydrogenase (ASA DH). The synthesis of this enzyme had been shown to be derepressed by growth in the presence of high concentrations of methionine. In the present work we have cloned and sequenced the HOM2 gene and found that the promoter region of this gene bears one copy of the consensus sequence for general control of amino acid synthesis. This prompted us to study the regulation of the expression of the HOM2 gene. We have found that ASA DH is the first reported enzyme of the related threonine and methionine pathway to be regulated by the general control of amino acid synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330954
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  • 5
    Electronic Resource
    Electronic Resource
    The synthesis of the two S-adenosyl-methionine synthetases is differently regulated in Saccharomyces cerevisiae (1991)
    Springer
    Molecular genetics and genomics 226 (1991), S. 224-232 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00273607
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  • 6
    Electronic Resource
    Electronic Resource
    The vacuolar compartment is required for sulfur amino acid homeostasis inSaccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 519-529 
    Details
    ISSN: 1617-4623
    Keywords: Sulfur metabolism ; Vacuolar biogenesis ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to isolate new mutations impairing transcriptional regulation of sulfur metabolism inSaccharomyces cerevisiae, we used a potent genetic screen based on a gene fusion expressing XylE (fromPseudomonas putida) under the control of the promoter region ofMET25. This selection yielded strains mutated in various different genes. We describe in this paper the properties of one of them,MET27. Mutation or disruption ofMET27 leads to a methionine requirement and affects S-adenosylmethionine (AdoMet)-mediated transcriptional control of genes involved in sulfur metabolism. The cloning and sequencing ofMET27 showed that it is identical toVPS33. Disruptions or mutations of geneVPS33 are well known to impair the biogenesis and inheritance of the vacuolar compartment. However, the methionine requirement ofvps33 mutants has not been reported previously. We show here, moreover, that other vps mutants of class C (no apparent vacuoles) also require methionine for growth. Northern blotting experiments revealed that themet27-1 mutation delayed derepression of the transcription of genes involved in sulfur metabolism. By contrast, this delay was not observed in amet27 disrupted strain. Physiological and morphological analyses ofmet27-1 andmet27 disrupted strains showed that these results could be explained by alterations in the ability of the vacuole to transport or store AdoMet, the physiological effector of the transcriptional regulation of sulfur metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583903
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  • 7
    Electronic Resource
    Electronic Resource
    Reactions of ε-Caprolactone with (Alkyne)zirconocene Complexes: Investigation of Elemental Steps in Catalytic Ring-Opening Polymerization of Lactones (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1351-1357 
    Details
    ISSN: 1434-1948
    Keywords: ε-Caprolactone complexes ; Zirconocene ; Ring-opening polymerization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of Cp2Zr(L)(η2-Me3SiC2SiMe3) (L = THF, pyridine) with ε-caprolactone, cyclohexanone and cycloheptanone result in an insertion of the carbonyl group into the zirconacyclopropene ring system of the alkyne complexes to yield the five-membered metallacyclic spiro-zirconadihydrofurane complexes 1, 3, 4. The product with ε-caprolactone is not stable at room temperature and was identified only by NMR spectra and chemical reactions. Starting from rac-(ebthi)Zr(η2-Me3SiC2SiMe3) with ε-caprolactone and ethylene carbonate under analogous conditions more stable complexes (2, 5) were obtained. Complexes 2 and 3 were characterized by X-ray crystal-structure analysis. Complexes 1 and 2 react with further ε-caprolactone in a catalytic ring-opening polymerization. The polymerization reactions were monitored by NMR spectroscopy.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Untypical Regioselectivity of Carbon Dioxide Coupling with Titanocene Complexes of Phenyl(trimethylsilyl)acetylene by Using the meso-1,2-Ethylene-1,1′-bis(η5-tetrahydroindenyl) Ligand System (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1495-1502 
    Details
    ISSN: 1434-1948
    Keywords: Alkyne complexes ; Titanium ; ansa-Metallocenes ; Carbon dioxide fixation ; C-C coupling ; Metallacycles ; Regioselectivity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of [meso-(ebthi)TiCl2] [ebthi = 1,2-ethylene-1,1′-bis(η5-tetrahydroindenyl)] with magnesium in the presence of the alkynes Me3SiC≡CSiMe3 and PhC≡CSiMe3 resulted in the formation of the complexes [meso-(ebthi)Ti(η2-Me3SiC2SiMe3)] (1) and [meso-(ebthi)Ti(η2-PhC2SiMe3)] (2a and 2b), which were isolated and then characterized by their NMR spectra. Due to incomplete reduction the TiIII complex [meso-(ebthi)Ti(THF)Cl] (3) was also obtained as a by-product of these reactions. By insertion into the Ti-CPh bond carbon dioxide reacted with the titanacyclopropene structure of the alkyne complex [meso-(ebthi)Ti(η2-PhC2SiMe3)] (2a), with untypical regioselectivity to yield the α-silyl-substituted meso-(ebthi)titanafuranone 6a. In the analogous reactions of the complexes [(thi)2Ti(η2-PhC2SiMe3)] (thi = η5-tetrahydroindenyl), [rac-(ebthi)Ti(η2-PhC2SiMe3)], and [Cp*2Ti(η2-PhC2SiMe3)] with carbon dioxide typical regioselectivity (insertion into the M-CSi bond of the titanacyclopropene) was observed, yielding the β-silyl-substituted titanafuranones 7, 8a, and 9. These results show that insertion of carbon dioxide into the M-C bond of the titanacyclopropene structure of the alkynemetallocene complexes is governed by the substitution pattern of the alkyne and the steric enviroment around the metal center. The complexes 3, 6a, and 7 were investigated by X-ray crystal structure analysis.
    Type of Medium: Electronic Resource
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  • 9
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    The structural basis for cancer drug interactions with the catalytic and allosteric sites of SAMHD1 (2018)
    National Academy of Sciences
    Details
    Publication Date: 2018-10-10
    Description: SAMHD1 is a deoxynucleoside triphosphate triphosphohydrolase (dNTPase) that depletes cellular dNTPs in noncycling cells to promote genome stability and to inhibit retroviral and herpes viral replication. In addition to being substrates, cellular nucleotides also allosterically regulate SAMHD1 activity. Recently, it was shown that high expression levels of SAMHD1 are also correlated with significantly worse patient responses to nucleotide analog drugs important for treating a variety of cancers, including acute myeloid leukemia (AML). In this study, we used biochemical, structural, and cellular methods to examine the interactions of various cancer drugs with SAMHD1. We found that both the catalytic and the allosteric sites of SAMHD1 are sensitive to sugar modifications of the nucleotide analogs, with the allosteric site being significantly more restrictive. We crystallized cladribine-TP, clofarabine-TP, fludarabine-TP, vidarabine-TP, cytarabine-TP, and gemcitabine-TP in the catalytic pocket of SAMHD1. We found that all of these drugs are substrates of SAMHD1 and that the efficacy of most of these drugs is affected by SAMHD1 activity. Of the nucleotide analogs tested, only cladribine-TP with a deoxyribose sugar efficiently induced the catalytically active SAMHD1 tetramer. Together, these results establish a detailed framework for understanding the substrate specificity and allosteric activation of SAMHD1 with regard to nucleotide analogs, which can be used to improve current cancer and antiviral therapies.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Abstracts of the 6th FECS Conference 1998 Lectures (1998)
    Springer
    Details
    Publication Date: 1998-09-01
    Print ISSN: 0944-1344
    Electronic ISSN: 1614-7499
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Springer
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