Search results for "Ras2"
showing 8 items of 8 documents
Role of saccharomyces cerevisiae nutrient signaling pathways during winemaking: a phenomics approach
2020
The ability of the yeast Saccharomyces cerevisiae to adapt to the changing environment of industrial processes lies in the activation and coordination of many molecular pathways. The most relevant ones are nutrient signaling pathways because they control growth and stress response mechanisms as a result of nutrient availability or scarcity and, therefore, leave an ample margin to improve yeast biotechnological performance. A standardized grape juice fermentation assay allowed the analysis of mutants for different elements of many nutrient signaling pathways under different conditions (low/high nitrogen and different oxygenation levels) to allow genetic-environment interactions to be analyze…
Mutant K-ras2 in serum
2003
Mutant tumour derived DNA has been detected in the sera of colorectal cancer patients. We investigated if mutant serum KRAS2 was detectable preoperatively in a large group of patients with colorectal neoplasia. A prospective study of 94 patients who underwent putative curative resection for colorectal carcinoma (CRC) was performed to ascertain if serum mutant KRAS2 could be used postoperatively as a disease marker.Preoperative sera from 78 patients were analysed (group A). Sera from 94 patients were obtained three monthly for up to three years during the postoperative period (group B). Codon 12 and 13 KRAS2 mutations were analysed in matched tumour and serum samples.In the preoperative grou…
Respiration and low cAMP-dependent protein kinase activity are required for high-level expression of the peroxisomal thiolase gene in Saccharomyces c…
1996
Transcription of genes for peroxisomal proteins is repressed by glucose and induced by oleate. At least for the peroxisomal thiolase gene (POT1) there is a third regulatory mechanism, mediated by the transcription factor Adr1p, which is responsible for the high-level expression of the gene in stationary phase. Here we show that a region in the POT1 promoter that extends from positions -238 to -152 mediates this mechanism, and we suggest that Adr1p acts indirectly on POT1. We have also analyzed the role of the cAMP-dependent protein kinase (PKA) in the transcriptional regulation of POT1. PKA exerts a negative control: the high, unregulated PKA activity in a bcy1 mutant maintains POT1 transcr…
Direct Identification of Each Specific Mutation in Codon 12 and 13 of ci-ki-ras2 by SSCP Analysis
1998
We compared the SSCP behaviour of the DNA fragments containing c-ki-ras 2 wild type 12 and 13 codons or each of the 12 possible point mutated sequences in these two codons. We found that a single electrophoresis condition was sufficient to distinguish each specific mutation from the other 11 and from the wild type sequence. This observation makes it possible to identify each specific mutation directly by SSCP without any need for reamplification and sequencing.
Role of glycine-82 as a pivot point during the transition from the inactive to the active form of the yeast Ras2 protein
1991
AbstractRas proteins bind either GDP or GTP with high affinity. However, only the GTP-bound form of the yeast Ras2 protein is able to stimulate adenylyl cyclase. To identify amino acid residues that play a role in the conversion from the GDP-bound to the GTP-bound state of Ras proteins, we have searched for single amino acid substitutions that selectively affected the binding of one of the two nucleotides. We have found that the replacement of glycine-82 of the Ras2 protein by serine resulted in an increased rate of dissociation of Gpp(NH)p, a nonhydrolysable analog of GTP, while the GDP dissociation rate was not significantly modified. Glycine-82 resides in a region that is highly conserve…
Energetic aspects of intramolecular coupling between the nucleotide binding site and the distal switch II region of the yeast RAS2 protein
1994
AbstractWe have studied the interaction of the yeast RAS2 protein with guanine nucleotides using energetic parameters for the dissociation of RAS·nucleotide complexes. The results indicated that a Gly → Ser substitution at position 82 led to an altered interaction with GppNHp and, to a lesser extent, also with GDP. It was also possible to conclude that structural perturbation of Gly82 can stimulate nucleotide release by decreasing the energetic barrier for nucleotide dissociation. This, together with the observation that residues 80 and 81 are involved in the response of RAS to nucleotide exchange factors without affecting GDP binding per se, suggests a potential mechanism for exchange fact…
Phosphorylation of an Overexpressed Yeast Ras2 Protein During the G1 Phase of the Cell Cycle
1994
RAS proteins regulate growth and differentiation in evolutionarily distant systems such as vertebrates and yeast (for reviews, see Tamanoi, 1988; Gibbs and Marshall, 1989; Broach and Deschenes, 1990). At the moleular level, a key function of the yeast RAS1 and RAS2 proteins (collectively referred to as RAS) is to positively regulate the production of cyclic AMP at the onset of the G1 phase of the cell cycle (Toda et al., 1985; De Vendittis et al., 1986). At this stage, RAS proteins are transiently activated by the noncovalent binding of a GTP molecule. Reversal of the effect occurs by the hydrolytic splitting of the ’γ-phosphate of GTP, that leaves a functionally inactive RASGDP complex, th…
RAS proteins and control of the cell cycle inSaccharomyces cerevisiae
1995
Genes related to the mammalian H-, K-, and N-ras oncogenes were identified in S. cerevisiae by DNA hybridization techniques (for reviews, see Tamanoi, 1988; Gibbs and Marshall, 1989; Broach and Deschenes, 1990). According to the rules of yeast genetics (dominant genes are indicated by three capital letters followed by a number), the yeast genes were denominated RAS1 and RAS2 (collectively referred to as RAS). The corresponding RAS1 and RAS2 proteins were 309 and 322 amino acids long, respectively. The sequence similarity between the human and yeast proteins was very high, reaching 90% identity at the level of the N-terminal 80 amino acids. As a consequence, perfect sequence conservation was…