The STE4 and STE18 genes are required for haploid yeast cell mating. Sequencing of the cloned genes revealed that the STE4 polypeptide shows extensive homology to the beta subunits of mammalian G proteins, while the STE18 polypeptide shows weak similarity to the gamma subunit of transducin. Null mutations in either gene can suppress the haploid-specific cell-cycle arrest caused by mutations in the SCG1 gene (previously shown to encode a protein with similarity to the alpha subunit of G proteins). We propose that the products of the STE4 and STE18 genes comprise the beta and gamma subunits of a G protein complex coupled to the mating pheromone receptors. The genetic data suggest pheromone-receptor binding leads to the dissociation of the alpha subunit from beta gamma (as shown for mammalian G proteins), and the free beta gamma element initiates the pheromone response.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|