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. 1985 Aug;82(15):4876–4880. doi: 10.1073/pnas.82.15.4876

Kinetics of redox-linked proton pumping activity of native and subunit III-depleted cytochrome c oxidase: a stopped-flow investigation.

P Sarti, M G Jones, G Antonini, F Malatesta, A Colosimo, M T Wilson, M Brunori
PMCID: PMC390460  PMID: 2410909

Abstract

The kinetics of oxidation of reduced cytochrome c by cytochrome c oxidase reconstituted into unilamellar vesicles (COV) has been followed by stopped-flow method in the time range 3 msec-1 sec. In the presence of valinomycin, the oxidation of cytochrome c is linked to proton ejection in the external medium, with an apparent stoichiometry (H+/e-) of 0.93 +/- 0.22, under conditions in which the enzyme is in the more active "pulsed" state (i.e., having undergone oxidation-reduction cycles). The time course of reaction indicates that the conformational change(s) involved in coupling the redox reaction to proton translocation is fast. Similar experiments carried out with cytochrome c oxidase depleted of subunit III show that proton-pumping is maintained, although with a lower efficiency (H+/e- = 0.5). The number of protons ejected per electron appears to be correlated to the value of the respiratory control ratio; although this result is partly due to an increase in the rate of diffusion back into the vesicles, a relationship between the respiratory control ratio and the efficiency of the proton pump may be inferred, suggesting a control of the H+/e-ratio.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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