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.

SSC1, an essential member of the yeast HSP70 multigene family, encodes a mitochondrial protein.

Abstract: SSC1 is an essential member of the yeast HSP70 multigene family (E. Craig, J. Kramer, and J. Kosic-Smithers, Proc. Natl. Acad. Sci. USA 84:4156-4160, 1987). Analysis of the SSC1 DNA sequence revealed that it could encode a 70,627-dalton protein that is more similar to DnaK, an Escherichia coli hsp70 protein, than other yeast hsp70s whose sequences have been determined. Ssc1p was found to have an amino-terminal extension of 28 amino acids, in comparison with either Ssa1p, another hsp70 yeast protein, or Dnak. This putative leader is rich in basic and hydroxyl amino acids, characteristic of many mitochondrial leader sequences. Ssc1p that was synthesized in vitro could be imported into mitochondria and was cleaved in the process. The imported protein comigrated with an abundant mitochondrial protein that reacted with hsp70-specific antibodies. We conclude that Ssc1p is a mitochondrial protein and that hsp70 proteins perform functions in many compartments of the cell.

Secretion of functional antibody and Fab fragment from yeast cells.

Abstract: We have constructed yeast strains that secrete functional mouse-human chimeric antibody and its Fab fragment into the culture medium For chimeric whole antibody, cDNA copies of the chimeric light-chain and heavy-chain genes of an anti-tumor antibody were inserted into vectors containing the yeast phosphoglycerate kinase promoter, invertase signal sequence, and phosphoglycerate kinase polyadenylylation signal Simultaneous expression of these genes in yeast resulted in secretion of properly folded and assembled chimeric antibody that bound to target cancer cells Yeast chimeric antibody exhibited antibody-dependent cellular cytotoxicity activity but not complement-dependent cytotoxicity activity For production of Fab fragments, a truncated heavy-chain (Fd) gene was created by introducing a stop codon near the codon for the amino acid at which papain digestion occurs Simultaneous expression of the resulting chimeric Fd and light-chain genes in yeast resulted in secretion of properly folded and assembled Fab fragment that bound to target cancer cells

Proline as a stress protectant in yeast: physiological functions, metabolic regulations, and biotechnological applications

Abstract: Proline is an important amino acid in terms of its biological functions and biotechnological applications. In response to osmotic stress, proline is accumulated in many bacterial and plant cells as an osmoprotectant. However, it has been shown that proline levels are not increased under various stress conditions in the yeast Saccharomyces cerevisiae cells. Proline is believed to serve multiple functions in vitro such as protein and membrane stabilization, lowering the T m of DNA, and scavenging of reactive oxygen species, but the mechanisms of these functions in vivo are poorly understood. Yeast cells biosynthesize proline from glutamate in the cytoplasm via the same pathway found in bacteria and plants and also convert excess proline to glutamate in the mitochondria. Based on the fact that proline has stress-protective activity, S. cerevisiae cells that accumulate proline were constructed by disrupting the PUT1 gene involved in the degradation pathway and by expressing the mutant PRO1 gene encoding the feedback inhibition-less sensitive γ-glutamate kinase to enhance the biosynthetic activity. The engineered yeast strains successfully showed enhanced tolerance to many stresses, including freezing, desiccation, oxidation, and ethanol. However, the appropriate cellular level and localization of proline play pivotal roles in the stress-protective effect. These results indicate that the increased stress protection is observed in yeast cells under the artificial condition of proline accumulation. Proline is expected to contribute to yeast-based industries by improving the production of frozen dough and alcoholic beverages or breakthroughs in bioethanol production.

Kinetics of growth and sugar consumption in yeasts

Abstract: An overview is presented of the steady- and transient state kinetics of growth and formation of metabolic byproducts in yeasts. Saccharomyces cerevisiae is strongly inclined to perform alcoholic fermentation. Even under fully aerobic conditions, ethanol is produced by this yeast when sugars are present in excess. This so-called 'Crabtree effect' probably results from a multiplicity of factors, including the mode of sugar transport and the regulation of enzyme activities involved in respiration and alcoholic fermentation. The Crabtree effect in S. cerevisiae is not caused by an intrinsic inability to adjust its respiratory activity to high glycolytic fluxes. Under certain cultivation conditions, for example during growth in the presence of weak organic acids, very high respiration rates can be achieved by this yeast. S. cerevisiae is an exceptional yeast since, in contrast to most other species that are able to perform alcoholic fermentation, it can grow under strictly anaerobic conditions. 'Non-Saccharomyces' yeasts require a growth-limiting supply of oxygen (i.e. oxygen-limited growth conditions) to trigger alcoholic fermentation. However, complete absence of oxygen results in cessation of growth and therefore, ultimately, of alcoholic fermentation. Since it is very difficult to reproducibly achieve the right oxygen dosage in large-scale fermentations, non-Saccharomyces yeasts are therefore not suitable for large-scale alcoholic fermentation of sugar-containing waste streams. In these yeasts, alcoholic fermentation is also dependent on the type of sugar. For example, the facultatively fermentative yeast Candida utilis does not ferment maltose, not even under oxygen-limited growth conditions, although this disaccharide supports rapid oxidative growth.

Structural and functional similarities between the SbcCD proteins of Escherichia coli and the RAD50 and MRE11 (RAD32) recombination and repair proteins of yeast

Abstract: The destruction of long palindromic DNA sequences in Escherichia coli is mediated by the products of sbcC and sbcD (Leach, 1994, BioEssays 16: 893-900). Mutations in these genes also function as co-suppressors with sbcB of recombination and repair defective recB or recC strains. The sbcB gene product is a 3' ~ 5' single-stranded DNA exonuclease. SbcC and SbcD proteins have ATPdependent double-stranded DNA exonuclease and ATPindependent single-stranded DNA endonuclease activities (J. C. Connelly and D. R. F. Leach, unpublished). Inactivation of these nucleases is proposed to achieve suppression of recBC by stabilizing DNA ends, allowing other recombination enzymes access in order to initiate recombination and DNA repair. Previous studies have shown structural similarities between E. coil SbcD and proteins from bacteriophages T4 (gp47), T5 (gpD12) and Bacillus subti/is (ORF3) (Leach et al., 1992, Genetica 87: 95-100; Sharpies and Lloyd, 1993, Nuc/Acids Res 21:2010). Bacteriophages T4 and T5 also have homologous equivalents of SbcC (T4 gp46 and T5 gpD13). In keeping with their relatedness to E. coli SbcCD, they are responsible for the exonuclease activities which normally degrade chromosomal DNA and are also important for phage replication, recombination and DNA repair. Recently it has been noted that a large number of diverse proteins that cleave phosphoester bonds share a common sequence structure. These enzymes include Ser/Thr protein phosphatases, diadenosine tetraphosphatases, 5' nucleotidases, 2',3'-cyclic phosphodiesterases, sphingomyelinases, an RNA lariat 2 ' -5 ' phosphodiesterase, and exonucleases; SbcD, gp47 and gpD12 belong to the latter group. The phosphoesterase signature sequence is DXH(~X25)GDXXD(~X25)GNHD/E (Zhuo et al., 1994, J Biol Chem 269: 26234-26238). We have noted an additional conserved motif (UUXGHXH, where U specifies a hydrophobic residue) located 84-153 amino acids from the GNHD/E sequence (Fig. 1A and data not shown). While this paper was in preparation we discovered that this fourth motif had also been independently identified (Yeast Update 3.6). Our particular interest focused on members of the phosphoesterase