Isolation of a gene for a regulatory 15‐kDa subunit of mitochondrial F₁F₀‐ATPase and construction of mutant yeast lacking the protein

A gene coding for yeast 15‐kDa protein, a regulatory factor of mitochondrial F₁F₀‐ATPase, was isolated. The cloned gene was disrupted in vitro and mutant strains that did not contain the 15‐kDa protein were constructed by transformation of yeast cells with the disrupted gene. The ATP‐synthesizing activity of the mutant mitochondria was the same as that of wild‐type cells, suggesting that the 15‐kDa protein is not required for mitochondrial oxidative phosphorylation. Collapse of the membrane potential induced ATP‐hydrolyzing activity of F₁F₀‐ATPase of the mutant mitochondria but not of normal mitochondria. Activation of the enzyme was also observed during incubation of submitochondrial particles from mutant cells, but not of those from wild‐type cells. Thus, it is inferred that the 15‐kDa protein supports the action of an intrinsic ATPase inhibitor of the ATP‐hydrolyzing activity of the enzyme upon de‐energization of mitochondrial membranes.