Substitutions in the pheromone-responsive Gbeta protein of Saccharomyces cerevisiae confer a defect in recovery from pheromone treatment.
The pheromone-responsive Galpha protein of Saccharomyces cerevisiae, Gpa1p, stimulates an adaptive mechanism that downregulates the mating signal. In a genetic screen designed to identify signaling elements required for Gpa1p-mediated adaptation, a large collection of adaptive-defective (Adp-) mutants were recovered. Of the 49 mutants characterized thus far, approximately three-quarters exhibit a dominant defect in the negative regulation of the pheromone response. Eight of the dominant Adp- mutations showed tight linkage to the gene encoding the pheromone-responsive Gbeta, STE4. Sequence analysis of the STE4 locus in the relevant mutant strains revealed seven novel STE4 alleles, each of which was shown to disrupt proper regulation of the pheromone response. Although the STE4 mutations had only minor effects on basal mating pathway activity, the mutant forms of Gbeta dramatically affected the ability of the cell to turn off the mating response after exposure to pheromone. Moreover, the signaling activity of the aberrant Gbetagamma subunits was suppressed by G322E, a mutant form of Gpa1p that blocks the pheromone response by sequestering Gbetagamma, but not by E364K, a hyperadaptive form of Gpa1p. On the basis of these observations, we propose that Gpa1p-mediated adaptation involves the binding of an unknown negative regulator to Gbetagamma.
Li
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Laboratory for Molecular Biology, University of Illinois at Chicago, 60607, USA.
Meldrum
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Stratton
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Stone
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DE
D000222:Adaptation, Physiological; D005656:Fungal Proteins / Q000235:genetics; D044385:GTP-Binding Protein alpha Subunits; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D044387:GTP-Binding Protein beta Subunits; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins; D000072235:Mating Factor; D008565:Membrane Proteins; D016296:Mutagenesis; D010455:Peptides / Q000494:pharmacology*; D010675:Pheromones / Q000494:pharmacology*; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D014158:Transcription, Genetic
C490024:FUS1 protein, S cerevisiae; D005656:Fungal Proteins; D044385:GTP-Binding Protein alpha Subunits; D044387:GTP-Binding Protein beta Subunits; D008565:Membrane Proteins; D010455:Peptides; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins; C067576:Ste4 protein, S cerevisiae; D000072235:Mating Factor; D019204:GTP-Binding Proteins; C084293:GPA1 protein, S cerevisiae; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins