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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 10 (1985), S. 103-110 
    ISSN: 1432-0983
    Keywords: Yeast taxonomy ; DNA homologies ; Southern analysis ; Glycolytic gene probes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genePDC1 ofSaccharomyces cerevisiae coding for pyruvate decarboxylase (E.C. 4.1.1.1.) was used as a hybridization probe to detect gene sequence homologies in different strains ofSaccharomyces cerevisiae and in other yeast species. Additionally six other genes coding for glycolytic enzymes as well as the genesURA3 of the pyrimidine synthetic andTRP1 of the tryptophan synthetic pathways were used. A restriction polymorphism for the BamH1 fragments carrying thePDC1 gene was evident within the speciesSaccharomyces cerevisiae. All strains definitely declared asSaccharomyces cerevisiae showed the same restriction patterns. Hybridizations of different intensities were observed only with species in the familySaccharomycetaceae. Hybridizations with different genes showed different degrees of conservation for certain DNA sequences.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Yeast DNA pools were prepared by ligating partial Sau3A genomic digests from strains carrying various MAL genes into the BamHI site of the yeast-Escherichia coli shuttle vector YRp7. They were used to transform recipient yeast strains that could not utilize maltose since they lacked a classical MAL gene. Transformants were obtained that could use maltose and also formed normal levels of maltase. They were unstable. They would lose the selective marker TRP1 of YRp7 alone, together with the ability to utilize maltose or only the ability to utilize maltose. The insertion of one of the plasmids was used as a hybridization probe for the others and found to share homologous sequences with all. They were then shown to contain the replication origin of the yeast 2 μm circle plasmid and additional genomic digests of total yeast DNA. They hybridized at various degrees of efficiency with several bands, indicating that they were part of a family of repeated sequences. Apparently, it was the combination of the replication origin of the 2 μm circles with the additional sequences that promoted maltose utilization.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Yeast mutants lacking phosphofructokinase activity because of a defect in one of the two genes PFK1 and PFK2 can still perform glycolysis and produce ethanol. However, they differ from normal wild-type yeast in several ways. After a transfer from a sugar-free to a glucose medium, wild-type cells start to produce ethanol right away, mutants only after a lag period of about 90 min. About two-thirds of the carbon atoms released as CO2 from wild-type cells derive from glucose carbon atoms 3 and 4. Mutants with a single defect in one of the two phosphofructokinase genes PFK1 and PFK2 show no such a preferential contribution of these two C-atoms of glucose. All six C-atoms contribute almost equally to CO2 production. We have isolated mutants that block glycolysis in single pfk1 and pfk2 mutants. They could be located in three different genes called BYP1, BYP2 and BYP3 (BYP for bypass). In a byp1 mutant, CO2 derived almost exclusively from C-atoms 3 and 4 of glucose. This is what the classical concept of yeast glycolysis predicts. During a search for metabolites accumulating in pfk and byp mutants, we found sedoheptulose-7-phosphate, a pentosephosphate cycle intermediate not detectable in wild-type cells. An analysis of enzymes acting in the direct oxidation of glucose-6-phosphate and in the pentosephosphate cycle did not show any defects in those activities. It is hypothesized that the pentosephosphate cycle not only functions, in providing phosphorylated derivatives of tetroses and pentoses for biosynthetic needs, but also plays an important role in sugar catabolism and fermentation. This hypothesis also implies that the reaction sequency catalyzed by phosphofructokinase and aldolase covers only part of the total catabolic flux.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mutants of Saccharomyces cerevisiae without detectable phosphofructokinase activity were isolated. They were partly recessive and belonged to two genes called PFK1 and PFK2. Mutants with a defect in only one of the two genes could not grow when they were transferred from a medium with a nonfermentable carbon source to a medium with glucose and antimycin A, an inhibitor of respiration. However, the same mutants could grow when antimycin A was added to such mutants after they had been adapted to the utilization of glucose. Double mutants with defects in both genes could not grow at all on glucose as the sole carbon source. Mutants with a single defect in gene PFK1 or PFK2 could form ethanol on a glucose medium. However, in contrast to wild-type cells, there was a lag period of about 2 h before ethanol could be formed after transfer from a medium with only nonfermentable carbon sources to a glucose medium. Wild-type cells under the same conditions started to produce ethanol immediately. Mutants with defects in both PFK genes could not form ethanol at all. Mutants without phosphoglucose isomerase or triosephosphate isomerase did not form ethanol either. Double mutants without phosphofructokinase and phosphoglucose isomerase accumulated large amounts of glucose-6-phosphate on a glucose medium. This suggested that the direct oxidation of glucose-6-phosphate could not provide a bypass around the phosphofructokinase reaction. On the other hand, the triosephosphate isomerase reaction was required for ethanol production. Experiments with uniformly labeled glucose and glucose labeled in positions 3 and 4 were used to determine the contribution of the different carbon atoms of glucose to the fermentative production of CO2. With only fermentation operating, only carbon atoms 3 and 4 should contribute to CO2 production. However, wild-type cells produced significant amounts of radioactivity from other carbon atoms and pfk mutants generated CO2 almost equally well from all six carbon atoms of glucose. This suggested that phosphofructokinase is a dispensable enzyme in yeast glycolysis catalyzing only part of the glycolytic flux.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1617-4623
    Keywords: Key wordsSaccharomyces cerevisiae ; Vesicular transport ; Golgi function ; Ypt/Rab GTPases ; Ypt suppressor mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ras-related, guanine nucleotide-binding proteins of the Ypt/Rab family play a key role at defined steps in vesicular transport, both in yeast and in mammalian cells. In yeast, Ypt1p has an essential function late in endoplasmic reticulum (ER) to Golgi transport, and the redundant Ypt31/Ypt32 GTPases have been proposed to act in transport through and/or from the Golgi. Here we report that mutant alleles of YPT31 and YPT32, whose gene products have a reduced affinity for GTP, are able to suppress the dominant lethal phenotype of YPT1 N121I . Co-expression of YPT1 N121I and the suppressor YPT31 N126I allow essentially undisturbed secretory transport in the absence of the respective wild-type GTPases. Such mutant cells massively overaccumulate 60–100 nm vesicles and are heat sensitive. It appears likely that the mutant GTPases, which are defective in nucleotide binding, compete for the binding of common interacting protein(s). These and other genetic interactions between YPT1, YPT31/32, ARF1 and SEC4 described here strongly support the view that Ypt31p and Ypt32p have a central, Golgi-associated function in anterograde or retrograde transport.
    Type of Medium: Electronic Resource
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