Differential effects of antimycin on ubisemiquinone bound in different environments in isolated succinate . cytochrome c reductase complex.

Abstract

Isolated succinate cytochrome c reductase complex from bovine heart mitochondria manifests a prominent g = 2.00 EPR signal attributable to ubisemiquinone.The ubisemiquinone signal can be formed by reduction of the complex with mixtures of succinate plus fumarate or by potentiometric titration in the presence of mediator dyes.The ubisemiquinone appears to be heterogeneous, consisting of at least two populations of stable semiquinone which can be distinguished on the basis of their different thermodynamic and EPR characteristics and their differential response to antimycin.The two different populations of ubisemiquinone contributing to the g = 2.00 EPR signal were selectively