Binding of citreoviridin to the beta subunit of the yeast F1-ATPase.

Citreoviridin, a nonfluorescent inhibitor of bovine and bacterial ATPases, also inhibits the yeast F1 (K1 = 2 microM). The beta subunit-specific fluorescent ligand, aurovertin, has been used to report the interaction of citreoviridin with the yeast F1-ATPase and the isolated beta subunit. Citreoviridin caused a marked decrease in the fluorescence increment associated with the binding of aurovertin to either intact F1 or the isolated beta subunit. Three lines of evidence indicate that citreoviridin and aurovertin bind to nonidentical sites on the beta subunit: 1) the binding of citreoviridin to the F1 or isolated beta subunit is noncompetitive with respect to aurovertin; 2) the number of aurovertin binding sites (Kd = 0.2 to 0.6 microM) per F1-ATPase molecule remains the same (1.89 +/- 0.6 mol of aurovertin bound per mol of F1) in the presence or absence of citreoviridin; 3) the F1-ATPase obtained from the aurovertin-resistant mutant aur-1 is partly inhibited by citreoviridin.