ASC1/RAS2 suppresses the growth defect on glycerol caused by the atp1-2 mutation in the yeast Saccharomyces cerevisiae.
To better define the regulatory role of the F(1)-ATPase alpha-subunit in the catalytic cycle of the ATP synthase complex, we isolated suppressors of mutations occurring in ATP1, the gene for the alpha-subunit in Saccharomyces cerevisiae. First, two atp1 mutations (atp1-1 and atp1-2) were characterized that prevent the growth of yeast on non-fermentable carbon sources. Both mutants contained full-length F(1)alpha-subunit proteins in mitochondria, but in lower amounts than that in the parental strain. Both mutants exhibited barely measurable F(1)-ATPase activity. The primary mutations in atp1-1 and atp1-2 were identified as Thr(383) --> Ile and Gly(291) --> Asp, respectively. From recent structural data, position 383 lies within the catalytic site. Position 291 is located near the region affecting subunit-subunit interaction with the F(1)beta-subunit. An unlinked suppressor gene, ASC1 (alpha-subunit complementing) of the atp1-2 mutation (Gly(291) --> Asp) restored the growth defect phenotype on glycerol, but did not suppress either atp1-1 or the deletion mutant Deltaatp1. Sequence analysis revealed that ASC1 was allelic with RAS2, a G-protein growth regulator. The introduction of ASC1/RAS2 into the atp1-2 mutant increased the F(1)-ATPase enzyme activity in this mutant when the transformant was grown on glycerol. The possible mechanisms of ASC1/RAS2 suppression of atp1-2 are discussed; we suggest that RAS2 is part of the regulatory circuit involved in the control of F(1)-ATPase subunit levels in mitochondria.
Mabuchi
T
T
Department of Biochemistry, Yamanashi Medical University, Tamaho, Nakakoma, Yamanashi 409-3898, Japan.
Ichimura
Y
Y
Takeda
M
M
Douglas
M G
MG
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000201:enzymology; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D019204:GTP-Binding Proteins; D005990:Glycerol / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D010641:Phenotype; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000201:enzymology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D018631:ras Proteins / Q000235:genetics* / Q000378:metabolism
C111825:ASC1 protein, S cerevisiae; D048868:Adaptor Proteins, Signal Transducing; D005656:Fungal Proteins; D046911:Macromolecular Substances; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins; D006180:Proton-Translocating ATPases; C489015:RAS2 protein, S cerevisiae; D018631:ras Proteins; D005990:Glycerol