Estimation of H+-translocation stoicheiometry of mitochondrial ATPase by comparison of proton-motive forces with clamped phosphorylation potentials in submitochondrial particles

The proton-motive forces generated in submitochondrial particles by both hydrolysis of ATP and oxidation of succinate have been measured by flow dialysis and compared with the ambient phosphorylation potentials. It is concluded that three H⁺ are translocated for each ATP molecule hydrolysed or synthesised. By utilising rat liver mitochondria respiring with β-hydroxybutyrate as a new system for regeneration of ATP from ADP and P_i, phosphorylation potentials were clamped at a range of values by using mixtures of particles and mitochondria in various ratios. As the rate of ATP hydrolysis by the particles was lowered, the proton-motive force decreased only slightly except at the very lowest rates, these results paralleling earlier studies on the relation between rate of respiration-driven proton translocation and proton-motive force.