Yeast

About: Yeast is a research topic. Over the lifetime, 31777 publications have been published within this topic receiving 868967 citations. The topic is also known as: yeasts.

Yeast KRE genes provide evidence for a pathway of cell wall beta-glucan assembly.

Abstract: The Saccharomyces cerevisiae KRE1 gene encodes a Ser/Thr-rich protein, that is directed into the yeast secretory pathway, where it is highly modified, probably through addition of O-linked mannose residues. Gene disruption of the KRE1 locus leads to a 40% reduced level of cell wall (1----6)-beta-glucan. Structural analysis of the (1----6)-beta-glucan fraction, isolated from a strain with a krel disruption mutation, showed that it had an altered structure with a smaller average polymer size. Mutations in two other loci, KRE5 and KRE6 also lead to a defect in cell wall (1----6)-beta-glucan production and appear to be epistatic to KRE1. These findings outline a possible pathway of assembly of yeast cell wall (1----6)-beta-glucan.

Genome-wide expression analyses: Metabolic adaptation of Saccharomyces cerevisiae to high sugar stress.

Abstract: The transcriptional response of laboratory strains of Saccharomyces cerevisiae to salt or sorbitol stress has been well studied. These studies have yielded valuable data on how the yeast adapts to these stress conditions. However, S. cerevisiae is a saccharophilic fungus and in its natural environment this yeast encounters high concentrations of sugars. For the production of dessert wines, the sugar concentration may be as high as 50% (w/v). The metabolic pathways in S. cerevisiae under these fermentation conditions have not been studied and the transcriptional response of this yeast to sugar stress has not been investigated. High-density DNA microarrays showed that the transcription of 589 genes in an industrial strain of S. cerevisiae were affected more than two-fold in grape juice containing 40% (w/v) sugars (equimolar amounts of glucose and fructose). High sugar stress up-regulated the glycolytic and pentose phosphate pathway genes. The PDC6 gene, previously thought to encode a minor isozyme of pyruvate decarboxylase, was highly induced under these conditions. Gene expression profiles indicate that the oxidative and non-oxidative branches of the pentose phosphate pathway were up-regulated and might be used to shunt more glucose-6-phosphate and fructose-6-phosphate, respectively, from the glycolytic pathway into the pentose phosphate pathway. Structural genes involved in the formation of acetic acid from acetaldehyde, and succinic acid from glutamate, were also up-regulated. Genes involved in de novo biosynthesis of purines, pyrimidines, histidine and lysine were down-regulated by sugar stress.

Engineering of Saccharomyces cerevisiae for efficient anaerobic alcoholic fermentation of L-arabinose.

Abstract: For cost-effective and efficient ethanol production from lignocellulosic fractions of plant biomass, the conversion of not only major constituents, such as glucose and xylose, but also less predominant sugars, such as L-arabinose, is required. Wild-type strains of Saccharomyces cerevisiae, the organism used in industrial ethanol production, cannot ferment xylose and arabinose. Although metabolic and evolutionary engineering has enabled the efficient alcoholic fermentation of xylose under anaerobic conditions, the conversion of L-arabinose into ethanol by engineered S. cerevisiae strains has previously been demonstrated only under oxygen-limited conditions. This study reports the first case of fast and efficient anaerobic alcoholic fermentation of L-arabinose by an engineered S. cerevisiae strain. This fermentation was achieved by combining the expression of the structural genes for the L-arabinose utilization pathway of Lactobacillus plantarum, the overexpression of the S. cerevisiae genes encoding the enzymes of the nonoxidative pentose phosphate pathway, and extensive evolutionary engineering. The resulting S. cerevisiae strain exhibited high rates of arabinose consumption (0.70 g h–1 g [dry weight]–1) and ethanol production (0.29 g h–1 g [dry weight]–1) and a high ethanol yield (0.43 g g–1) during anaerobic growth on L-arabinose as the sole carbon source. In addition, efficient ethanol production from sugar mixtures containing glucose and arabinose, which is crucial for application in industrial ethanol production, was achieved.

Silent information regulator protein complexes in Saccharomyces cerevisiae: A SIR2/SIR4 complex and evidence for a regulatory domain in SIR4 that inhibits its interaction with SIR3

Abstract: The SIR2, SIR3, and SIR4 silent information regulator proteins are involved in the assembly of silent chromatin domains in the budding yeast Saccharomyces cerevisiae. Using a series of biochemical experiments, we have studied protein–protein interactions involving these proteins. We found that yeast extracts contained a SIR2/SIR4 complex that was associated with little or no SIR3. However, truncations of the N-terminal two-thirds of the SIR4 protein allowed it to efficiently associate with SIR3, suggesting that the N-terminal domain of SIR4 inhibited its interaction with SIR3. We propose that the SIR3 and SIR4 proteins interact only during the assembly of the SIR protein complex at the silencer and that an early step in assembly unmasks the SIR4 protein to allow its association with SIR3. To test whether the interactions observed in yeast extracts were direct, we tested these SIR-SIR interactions using bacterially expressed SIR proteins. We observed direct interactions between SIR4 and SIR2, SIR4 and SIR3, SIR2 and SIR3, SIR2 and SIR2, and SIR4 and SIR4, indicating that the associations observed in yeast extracts were direct.