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.

Kinetics of redox-linked proton pumping activity of native and subunit III-depleted cytochrome c oxidase: a stopped-flow investigation / Sarti, Paolo; M. G., Jones; G., Antonini; Malatesta, Francesco; Colosimo, Alfredo; M. T., Wilson; Brunori, Maurizio. - In: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - ISSN 0027-8424. - 82:(1985), pp. 4876-4880. [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.

SARTI, Paolo;MALATESTA, FRANCESCO;COLOSIMO, Alfredo;BRUNORI, Maurizio
1985

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.
1985
Membrane Potentials; Mitochondria
01 Pubblicazione su rivista::01a Articolo in rivista
Kinetics of redox-linked proton pumping activity of native and subunit III-depleted cytochrome c oxidase: a stopped-flow investigation / Sarti, Paolo; M. G., Jones; G., Antonini; Malatesta, Francesco; Colosimo, Alfredo; M. T., Wilson; Brunori, Maurizio. - In: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - ISSN 0027-8424. - 82:(1985), pp. 4876-4880. [10.1073/pnas.82.15.4876]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/459103
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