Zn2+ binding to the cytoplasmic side of Paracoccus denitrificans cytochrome c oxidase selectively uncouples electron transfer and proton translocation1
Open Access
- 14 August 2001
- journal article
- Published by Wiley in FEBS Letters
- Vol. 503 (2-3) , 142-146
- https://doi.org/10.1016/s0014-5793(01)02719-3
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.Keywords
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