Inhibition of the ATPase activity of Escherichia coli ATP synthase by magnesium fluoride

Inhibition of ATPase activity of Escherichia coli ATP synthase by magnesium fluoride (MgFx) was studied. Wild-type F1-ATPase was inhibited potently, albeit slowly, when incubated with MgCl2, NaF, and NaADP. The combination of all three components was required. Reactivation of ATPase activity, after removal of unbound ligands, occurred with half-time of ∼14 h at 22 °C and was quasi-irreversible at 4 °C. Mutant F1-ATPases, in which catalytic site residues involved in transition state formation were modified, were found to be resistant to inhibition by MgFx. The data demonstrate that MgFx in combination with MgADP behaves as a tight-binding transition state analog in E. coli ATP synthase.