Induction and Repression of Mitochondrial ATPase in Yeast

A simple mechanical procedure for the preparation of particle‐bound Mg‐ATPase is described. It represented at least 80% of total ATPase activity, both in the case of aerobically and of anaerobically grown yeast. When analyzed in a sucrose gradient, ATPase from aerobic yeast sedimented with NADH‐oxidase. ATPase from aerobic or anaerobic yeast showed 2 pH optima, as had been described for ATPase localized in carefully prepared and purified yeast mitochondria. Particle‐bound ATPase from aerobic or anaerobic yeast showed pronounced oligomycin sensitivity. Anaerobically grown yeast synthesized particle‐bound Mg‐ATPase at the low basal rate of 7–10 μmoles P/10 min/mg protein. During O2‐induction without growth, respiratory enzymes and ATPase were induced simultaneously. Both inductions were inhibited by acti‐dione. Aerobically grown, glucose‐repressed yeast synthesized ATPase at a rate similar to anaerobic yeast. Progressive derepression during growth produced a simultaneous increase of the rate of cell respiration (30–270) and of ATPase activity (10–60). Ethanol‐grown cells had a constant high Qo2 and synthesized ATPase at the high constant rate of 60. Regulation of ATPase synthesis was strictly identical when activity was measured at the two pH optima, suggesting the presence of a single mitochondrial ATPase. The possibility of separate phosphorylating and hydrolytic sites on the enzyme is discussed.