The N terminus of Saccharomyces cerevisiae Sst2p plays an RGS-domain-independent, Mpt5p-dependent role in recovery from pheromone arrest.
The Saccharomyces cerevisiae RGS protein Sst2p is involved in desensitization to pheromone and acts as a GTPase-activating protein for the Galpha subunit Gpa1p. Other results indicate that Sst2p acts through Mpt5p and that this action occurs downstream of Fus3p and through Cln3p/Cdc28p. Our results indicate that the interaction of Sst2p with Mpt5p requires the N-terminal MPI (Mpt5p-interacting) domain of Sst2p and is independent of the C-terminal RGS domain. Overexpression of the MPI domain results in an Mpt5p-dependent increase in recovery from pheromone arrest. Overexpression of either intact Sst2p or the MPI domain leads to partial suppression of a gpa1 growth defect, and this suppression is dependent on Mpt5p, indicating that MPI function occurs downstream of Gpa1p and through Mpt5p. Combination of an mpt5 mutation with the GPA1(G302S) mutation, which uncouples Gpa1p from Sst2p, results in pheromone supersensitivity similar to the sst2 mutant, and promotion of recovery by overexpression of Sst2p is dependent on both Mpt5p and the Gpa1p interaction. These results indicate that Sst2p is a bifunctional protein and that the MPI domain acts through Mpt5p independently of the RGS domain. RGS family members from other fungi contain N-terminal domains with sequence similarity to the Sst2p MPI domain, suggesting that MPI function may be conserved.
Xu
B E
BE
Department of Microbiology and Molecular Genetics and the Vermont Cancer Center, University of Vermont, College of Medicine, Burlington, Vermont 05405-0068, USA.
Skowronek
K R
KR
Kurjan
J
J
D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins; D004926:Escherichia coli / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry* / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020690:GTPase-Activating Proteins / Q000378:metabolism; D005800:Genes, Fungal; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010641:Phenotype; D010675:Pheromones / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D020710:RGS Proteins / Q000737:chemistry*; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D044385:GTP-Binding Protein alpha Subunits; D020690:GTPase-Activating Proteins; C449502:MPT5 protein, S cerevisiae; D010675:Pheromones; D020710:RGS Proteins; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; C094301:SST2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C075580:FUS3 protein, S cerevisiae; D020928:Mitogen-Activated Protein Kinases; C084293:GPA1 protein, S cerevisiae; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins