Role of cooperative H+/e− Linkage (redox Bohr effect) at heme a/CuA and heme a3/CuB in the proton pump of cytochrome c oxidase
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It is a pleasure to contribute to the special issue published in honor of Vladimir Skulachev, a distinguished scientist who greatly contributes to maintain a high standard of biochemical research in Russia. A more particular reason can be found in his work (Artzabanov, V. Y., Konstantinov, A. A., and Skulachev, V. P. (1978) FEBS Lett., 87, 180–185), where observations anticipating some ideas presented in my article were reported. Cytochrome c oxidase exhibits protonmotive, redox linked allosteric cooperativity. Experimental observations on soluble bovine cytochrome c oxidase are presented showing that oxido-reduction of heme a/CuA and heme a3/CuB is linked to deprotonation/protonation of two clusters of protolytic groups, A1 and A2, respectively. This cooperative linkage (redox Bohr effect) results in the translocation of 1 H+/oxidase molecule upon oxido-reduction of heme a/CuA and heme a3/CuB, respectively. Results on liposome-reconstituted oxidase show that upon oxidation of heme a/CuA and heme a3/CuB protons from A1 and A2 are released in the outer aqueous phase. A1 but not A2 appears to take up protons from the inner aqueous space upon reduction of the respective redox center. A cooperative model is presented in which the A1 and A2 clusters, operating in close sequence, constitute together the gate of the proton pump in cytochrome c oxidase.