The mechanism of inhibition by oligomycin of oxidative phosphorylation in mitochondria

1. The concentration of specific oligomycin-binding sites in rat-liver mitochondria is 0.12 nmole/mg protein, whereas at least 10-times more oligomycin can be bound non-specifically. 2. The activity of oligomycin-inhibited processes in intact mitochondria and submitochondrial particles cannot be restored by treatment with egg lecithin or mitochondrial phospholipids. 3. Analysis of the kinetics of inhibition of State-3 respiration by oligomycin reveals that (i) after a certain lag period the inhibition by oligomycin is pseudo-first order with respect to the respiratory-control ratio, defined as the ratio of the respiratory rate at time t to that of the final inhibited site, (ii) the value of the pseudo-first-order rate constant (k0) is dependent on the oligomycin: protein ratio, phospholipid: protein ratio, pH and temperature, (iii) the effects of various substrates and inhibitors of electron transfer on the kinetics of oligomycin inhibition can be explained by their effects on respiratory control. 4. A detailed model is proposed for the interaction of oligomycin with mitochondria. It is proposed that two conformations of the oligomycin-sensitive site are present, and that oligomycin specifically binds to the conformation that is involved in the induction of respiratory control.