Activity of proteoliposomes containing cytochrome oxidase in the submitochondrial orientation

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Abstract
Cytochrome‐c oxidase proteoliposomes containing internally trapped cytochrome c can turn over on internal or external cytochrome c. At low TMPD levels the internal activity is significantly lower than the external activity as the functional internal cytochrome c is not fully reduced in the steady state. Increasing TMPD concentration increases the internal rate to equal that of the external enzyme. Internal activity results in the accumulation of TMPD+. Valinomycin increases this accumulation and subsequently FCCP decreases it. In the presence of excess external cytochrome c, the effects of these ionophores are reversed. The internally‐facing enzyme is thus capable of generating a ΔμH+ in proteoliposomes as well as in submitochondrial particles.