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Zn2+ binding to the cytoplasmic side of Paracoccus denitrificans cytochrome c oxidase selectively uncouples electron transfer and proton translocation

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Kannt,  Aimo
Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Ostermann,  Thomas
Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Müller,  Hannelore
Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Ruitenberg,  Maarten
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Kannt, A., Ostermann, T., Müller, H., & Ruitenberg, M. (2001). Zn2+ binding to the cytoplasmic side of Paracoccus denitrificans cytochrome c oxidase selectively uncouples electron transfer and proton translocation. FEBS Letters, 503(2-3), 142-146. doi:10.1016/S0014-5793(01)02719-3.


Cite as: https://hdl.handle.net/21.11116/0000-0007-0B0E-F
Abstract
Using a combination of stopped-flow spectrophotometric proton pumping measurements and time-resolved potential measurements on black lipid membranes, we have investigated the effect of Zn2+ ions on the proton transfer properties of Paracoccus denitrificans cytochrome c oxidase. When zinc was enclosed in the interior of cytochrome c oxidase containing liposomes, the H/e stoichiometry was found to gradually decrease with increasing Zn2+ concentration. Half-inhibition of proton pumping was observed at [Zn2+]i=75 μM corresponding to about 5–6 Zn2+ ions per oxidase molecule. In addition, there was a significant increase in the respiratory control ratio of the proteoliposomes upon incorporation of Zn2+. Time-resolved potential measurements on a black lipid membrane showed that the electrogenic phases slowed down in the presence of Zn2+ correspond to phases that have been attributed to proton uptake from the cytoplasmic side and to proton pumping. We conclude that Zn2+ ions bind close to or within the two proton transfer pathways of the bacterial cytochrome c oxidase.