ATP synthesis and hydrolysis in submitochondrial particles subjected to an acid-base transition. Effects of the ATPase inhibitor protein.

ATP hydrolysis or succinate oxidation by inhibitor-rich submitochondrial particles leads to a 3-fold increase in ATPase activity, with concomitant loss of about 30% of bound inhibitor protein. An acid-base transition causes similar, but smaller, effects (a 30% ATPase increase, and a loss of 8% of the inhibitor). Omitting the electrical component of the gradient completely abolished these effects. The inhibitor protein inhibits ADP phosphorylation induced by an acid-base transition but not by NADH oxidation. This is suggested to reflect the slow movement of the inhibitor protein and the brief period of acid-base jump phosphorylation.