In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 82, No. 15 ( 1985-08), p. 4876-4880
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.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.82.15.4876
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
1985
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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