Coenzyme Q induces GDP-sensitive proton conductance in kidney mitochondria

Addition of coenzyme Q(10) (CoQ) at low concentration (29 nmol/mg of protei n) to kidney but not liver mitochondria resulted in an increase in proton c onductance. This uncoupling activity required fatty acid and was completely inhibited by GDP. CoQ activated when it was likely to be reduced but not w hen it was likely to become oxidized. However, the redox state of endogenou s CoQ did not affect mitochondrial proton conductance. Stimulation by CoQ w as not inhibited by cyclosporin A, carboxyatractylate, bongkrekate and cata lase but could be reversed by superoxide dismutase. We conclude that CoQ ac ted in mitochondria through production of superoxide, which mediated uncoup ling, probably by acting through uncoupling protein 2.