Oxidative phosphorylation in yeast III. ATPase activity of the mitochondrial fraction from a cytoplasmic respiratory-deficient mutant

Abstract

1. Mitochondria were isolated from a cytoplasmic respiratory-deficient variant of yeast Saccharomyces carlsbergensis NCYC 74. 2. Mg 2+-dependent ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity of the mitochondrial fraction displayed two pH optima, at pH 6.2 and 9.5. The activity at pH 6.2 corresponded closely to that found in non-mutant yeast. The specific activity of the reaction at pH 9.5 was lower than in wild-yeast mitochondria and, unlike wild-type yeast ATPase, was resistant to oligomycin inhibition. 3. The possibility is discussed that the ATPase activity of the mutant mitochondria may represent a preserved part of the oxidative phosphorylation system either structurally modified or lacking a component which would make it oligomycin sensitive.