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  • Organic Chemistry  (29)
  • Saccharomyces cerevisiae  (10)
  • Calcium  (5)
  • 1990-1994  (43)
  • 1880-1889  (1)
  • 1
    ISSN: 0170-2041
    Keywords: Housane ; Norcaradiene ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloaddition of a Very Reactive Cyanovinylcarbene with Benzene and 3,4-Dichlorocyclobutene. Molecular and Crystal Structure of 2,3-Dichloro-5-(1-cyano-2-methyl-1-propenyl)-5-housanecarbonitrile and 7-(1-Cyano-2-methyl-1-propenyl)-7-norcaradienecarbonitrileThe cyanovinylcarbene 2 has been generated by photolysis of 3,3-dimethyl-3H-pyrazole-4,5-dicarbonitril (1) and the cycloaddition products with benzene and with 3,4-dichlorocyclobutene have been isolated. The molecular structures of the cycloaddition products 7-(1-cyano-2-methyl-1-propenyl)-7-norcaradienecarbonitrile (3) and 2,3-dichloro-5-(1-cyano-2-methyl-1-propenyl)-5-housanecarbonitrile (4) were determined by X-ray analyses. The bridging bond of the bicyclo[2.1.0]pentane group in 4 is shortened to 1.515 Å by the electronic interaction of this group with the cyano substituent. The vinyl substituent has no influence because of perpendicular orientation.
    Additional Material: 2 Ill.
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  • 2
    ISSN: 1432-2013
    Keywords: Renal proximal tubule ; Intracellular calcium ; Calcium influx ; Primary culture ; Calcium store depletion ; 86Rb efflux ; Calcium ; sensitive potassium channels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cytoplasmic calcium changes and calcium influx evoked by adenosine triphosphate (ATP) were investigated in primary cultures of rabbit proximal convoluted tubule cells. Extracellular ATP (50 μM) induced a biphasic increase of [Ca2+]i measured with the calcium probe fura-2. In the early phase, the mobilization of intracellular pools resulted in a transient increase of [Ca2+]i from 106±11 nM (n=36) to 1059±115% (n=29) of the resting level within 10 s. In the presence of external calcium, [Ca2+]i then decreased within 3 min to a sustained level (398±38%,n=8). Measurements of fura-2 quenching by external manganese revealed that this phase was the result of an increased Ca2+ uptake, blocked by lanthanum (10 μM) and verapamil (100 μM) but not by the nifedipin (25 μM). Internal calcium store depletion by ATP induced an increased calcium influx through lanthanum- and verapamil-sensitive, nifedipininsensitive calcium channels, located on the apical membrane of the cells. As indicated by86Rb+ efflux measurements, ATP activated a potassium efflux that was blocked by barium andLeiurus quinquestriatus hebraeus (LQH) venom (containing charybdotoxin) indicating the involvement of Ca2+-sensitive K+ channels. Moreover, in the presence of the LQH venom, the internal calcium stores were not replenished after being depleted by ATP. Our results indicate that an ATPevoked hyperpolarization of the plasma membrane leads to increased Ca2+ influx, which facilitates the replenishment of the internal stores.
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  • 3
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Cell cycle ; Proline ; DNA sequencing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report here the isolation of temperature-sensitive mutants of the yeast Saccharomyces cerevisiae which exhibit cdc phenotypes. The recessive mutations defined four complementation groups, named ore1, ore2, ore3 and ore4. At the non-permissive temperature, strains bearing these mutations arrested in the G1 phase of the cell cycle. The wild-type allele of the gene altered in ore2 mutants was cloned. The nucleotide sequence of a fragment which can complement the mutation showed the presence of an open reading frame capable of encoding a protein with 286 amino acid residues. The deduced amino acid sequence showed 25% identity with that of the Escherichia coli Δ1-pyrroline-5-carboxylate reductase, an enzyme of the pathway for the biosynthesis of proline. The ore2 mutants, correspondingly, were found to be capable of growing at the non-permissive temperature on a synthetic medium supplemented with proline. In addition, the chromosomal location of the gene and its restriction map were compatible with those previously reported for the PRO3 gene which encodes the S. cerevisiae Δ1-pyrroline-5-carboxylate reductase.
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  • 4
    ISSN: 0749-503X
    Keywords: RVS161 gene ; Saccharomyces cerevisiae ; stationary phase entry ; viability loss ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In yeast, nutrient starvation leads to entry into stationary phase. Mutants that do not respond properly to starvation conditons have been isolated in Saccharomyces cerevisiae. Among them the rvs161 mutant (RVS for Reduced Viability upon Starvation) is sensitive to carbon, nitrogen and sulphur starvation. When these nutrients are depleted in the medium, mutant cells show cellular viability loss with morphological changes. The mutation rvs161-1 is very pleiotropic, and besides the defects in stationary phase entry, the mutant strain presents other alterations: sensitivity to high salt concentrations, hypersensitivity to amino acid analogs, no growth on lactate or acetate medium. The addition of salts or amino acid analogs leads to the same morphological defects observed in starved cells, suggesting that the gene could be implicated mainly in the control of cellular viability. The gene RVS161 was cloned; it codes for a 30,252 daltons protein. No homology was detected with the proteins contained in the databases. Moreover, Southern analysis revealed the presence of other sequences homologous to the RVS161 gene in the yeast genome.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 9 (1993), S. 495-506 
    ISSN: 0749-503X
    Keywords: Nuclear migration ; protein repeats ; cell cycle ; Saccharomyces cerevisiae ; nutrient starvation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have isolated a mutant (rvs272) of the yeast (Saccharomyces cerevisiae) that displays an altered phenotype in stationary phase. It shows a high proportion of large-budded cells with two non-segregated nuclei staying in the mother cell. This phenotype is also expressed in various conditions when cells are synchronized, energy depleted or treated with the antimitotic drug benomyl. The RVS272 gene has been identified as the NUM1 gene already described. This gene presents a 192 bp tandemly repeated motif and we show that the number of repeats can vary from 1 to about 24 among different strains, without apparently affecting the function of the encoded protein. We suggest that this protein could be involved in polymerization catalysis and/or stabilization of microtubules.
    Additional Material: 8 Ill.
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  • 6
    ISSN: 0749-503X
    Keywords: Chromosome III ; Saccharomyces cerevisiae ; mating type ; HML ; BUD5 ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: This paper reports the DNA sequence of a segment of 9·8 kb of the chromosome III. The sequenced DNA contains the MATα locus. The new sequence of the MATα locus differs from the previously reported sequence by six modifications in the W segment. We have found the same modifications in the HML locus. The corrected sequence contains, in HML, an open reading frame (ORF) of 190 codons which ends at the border between the W segment and the flanking DNA. In the MAT locus, this ORF extends in the flanking DNA up to 538 codons. This ORF corresponds to a gene independently identified as BUD5 (Chant et al., 1991). This gene presents homologies with the exchange factors SDC25 and CDC25. A large ORF of 1399 codons is found on the opposite side of MATα (toward the telomere). This ORF corresponds to a new gene YCR724. Next to this gene is a small ORF, YCR725, of 127 codons. The localization of this fragment on chromosome III, originally supposed to be distal from the MAT locus based on genetic distance, illustrates variation in recombination frequency along the chromosome and suggests the existence of hot spots of recombination between MAT and the THR4 locus.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 8
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Translation ; Splicing ; Paromomycin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The MSS51 gene product has been previously shown to be involved in the splicing of the mitochondrial pre-mRNA of cytochrome oxidase subunit I (COX1). We show here that it is specifically required for the translation of the COX1 mRNA. Furthermore, the paromomycin-resistance mutation (P inf454 supR ) which affects the 15 S mitoribosomal RNA, interferes, directly or indirectly, with the action of the MSS51 gene product. Possible roles of the MSS51 protein on the excision of COX1 introns are discussed.
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  • 9
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Cell cycle ; Bud site selection ; Guanine exchange factor ; Ras
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Guanine Exchange Factor (GEF) activity for Ras proteins has been associated with a conserved domain in Cdc25p, Sdc25p in Saccharomyces cerevisiae and several other proteins recently found in other eukaryotes. We have assessed the structure-function relationships between three different members of this family in S. cerevisiae, Cdc25p, Sdc25p and Bud5p. Cdc25p controls the Ras pathway, whereas Bud5p controls bud site localization. We demonstrate that the GEF domain of Sdc25p is closely related to that of Cdc25p. We first constructed a thermosensitive allele of SDC25 by specifically altering amino acid positions known to be changed in the cdc25-1 mutation. Secondly, we constructed three chimeric genes from CDC25 and SDC25, the products of which are as active in the Ras pathway as are the wild-type proteins. In contrast, similar chimeras made between CDC25 and BUD5 lead to proteins that are inactive both in the Ras and budding control pathways. This difference in the ability of chimeric proteins to retain activity allows us to define two subclasses of structurally different GEFs: Cdc25p and Sdc25p are Ras-specific GEFs, and Bud5p is a putative GEF for the Rsr1/Bud1 Rap-like protein.
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  • 10
    ISSN: 0170-2041
    Keywords: Fungal metabolites ; Spiro acetals ; Antifungal agents ; Palmarumycins CP ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four new penta- and hexacyclic antifungal and antibacterial metabolites, the palmarumycins CP1-CP4 (1-4), were isolated from Coniothyrium palmarum. In these structurally unique antibiotics, a 1,8-dihydroxynaphthalene unit is connected by a spiroacetal to another partially reduced naphthalene unit. The structure of the pentacyclic palmarumycin CP3 (3) was confirmed by X-ray structure analysis.
    Additional Material: 1 Ill.
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