Saccharomyces cerevisiae putative G protein, Gtr1p, which forms complexes with itself and a novel protein designated as Gtr2p, negatively regulates the Ran/Gsp1p G protein cycle through Gtr2p.
Prp20p and Rna1p are GDP/GTP exchanging and GTPase-activating factors of Gsp1p, respectively, and their mutations, prp20-1 and rna1-1, can both be suppressed by Saccharomyces cerevisiae gtr1-11. We found that gtr1-11 caused a single amino acid substitution in Gtr1p, forming S20L, which is a putative GDP-bound mutant protein, while Gtr1p has been reported to bind to GTP alone. Consistently, gtr1-S20N, another putative GDP-bound mutant, suppressed both prp20-1 and rna1-1. On the other hand, gtr1-Q65L, a putative GTP-bound mutant, was inhibitory to prp20-1 and rna1-1. Thus, the role that Gtr1p plays in vivo appears to depend upon the nucleotide bound to it. Our data suggested that the GTP-bound Gtr1p, but not the GDP-bound Gtr1p, interacts with itself through its C-terminal tail. S. cerevisiae possesses a novel gene, GTR2, which is homologous to GTR1. Gtr2p interacts with itself in the presence of Gtr1p. The disruption of GTR2 suppressed prp20-1 and abolished the inhibitory effect of gtr1-Q65L on prp20-1. This finding, taken together with the fact that Gtr1p-S20L is a putative, inactive GDP-bound mutant, implies that Gtr1p negatively regulates the Ran/Gsp1p GTPase cycle through Gtr2p.
Nakashima
N
N
Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka 812-8582, Japan.
Noguchi
E
E
Nishimoto
T
T
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D020931:ran GTP-Binding Protein
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C080324:GSP1 protein, S cerevisiae; C121263:GTR2 protein, S cerevisiae; C121262:Gtr1 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; C067050:SRM1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D020559:Monomeric GTP-Binding Proteins; D020931:ran GTP-Binding Protein