Kinetics of oxidative phosphorylation in Paracoccus denitrificans. 2. Evidence for a kinetic and thermodynamic modulation of F0F1-ATPase by the activity of the respiratory chain.

(1) The affinity of the F0F1-ATPase from Paracoccus denitrificans for ATP during NADH-driven oxidative phosphorylation has been analyzed under different conditions by examining the type and extent of product inhibition. (2) A limited collapse of the protonmotive force (delta p) due to partial uncoupling does not increase the affinity for ATP at the active site(s) of the enzyme; instead, a partial noncompetitive inhibition becomes apparent, compatible with the binding of ATP to a noncatalytic site (or sites) with high affinity. (3) In contrast, partial inhibition of the electron-transport chain increases the extent of pure competitive product inhibition and, therefore, the affinity for ATP at the active site(s). (4) The results are interpreted as indicative of a modulation of the rate of ATP release from the active site(s) of the F0F1-ATPase which is controlled by the activity of the electron-transport chain and not by delta p.