title: The STE4 and STE18 genes of yeast encode potential beta and gamma subunits of the mating factor receptor-coupled G protein.
abstract: 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.
authors.affiliation: Genetic Engineering Section NRC Biotechnology Research Institute, Montreal, Quebec, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Whiteway
authors.forename: L
authors.initials: L
authors.lastname: Hougan
authors.forename: D
authors.initials: D
authors.lastname: Dignard
authors.forename: D Y
authors.initials: DY
authors.lastname: Thomas
authors.forename: L
authors.initials: L
authors.lastname: Bell
authors.forename: G C
authors.initials: GC
authors.lastname: Saari
authors.forename: F J
authors.initials: FJ
authors.lastname: Grant
authors.forename: P
authors.initials: P
authors.lastname: O'Hara
authors.forename: V L
authors.initials: VL
authors.lastname: MacKay
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D005796:Genes; D005800:Genes, Fungal; D006238:Haploidy; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009154:Mutation; D011956:Receptors, Cell Surface / Q000235:genetics*; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors; D015293:Transducin / Q000235:genetics*; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D046911:Macromolecular Substances; D011956:Receptors, Cell Surface; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide; D014157:Transcription Factors; D001616:beta-Galactosidase; D015293:Transducin