Mechanism of control of cytochrome oxidase activity by the electrochemical-potential gradient.

Cytochrome c oxidation by bovine cytochrome oxidase embedded into liposomal vesicles with high respiratory control ratio (RCR = 6-10) has been studied by rapid-mixing experiments in the presence and absence of different ionophores. Kinetic analysis of the reaction indicates a linkage between the intrinsic activity of the enzyme, the efficiency of coupling and the electrochemical potential across the membrane. A simple model, based on two allosteric states with different catalytic properties in rapid equilibrium, is presented and successfully applied in the simulation of the observed time-course.