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Electron Transfer from Cytochrome c to 8-azido-ATP-Modified Cytochrome c Oxidase

Lin, Jian and Wu, Shuguang and Chan, Sunney I. (1995) Electron Transfer from Cytochrome c to 8-azido-ATP-Modified Cytochrome c Oxidase. Biochemistry, 34 (19). pp. 6335-6343. ISSN 0006-2960. doi:10.1021/bi00019a011.

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Bovine heart cytochrome c oxidase (CcO) has been modified by 8-azido-adenosine 5'- triphosphate (8-azido-ATP), and the electron-transfer activity from ferrocytochrome c to the modified CcO under physiological ionic strengths has been studied by the laser flash photolysis technique with 5-deazariboflavin and EDTA as the electron donor. The kinetics of intermolecular electron transfer between the redox protein partners was shown to be reduced significantly. In addition, there is significant decrease in the binding affinity of the cytochrome c to the oxidase upon 8-azido-ATP modification. The 8-azido-ATP-modified CcO exhibited 50% of the intracomplex electron-transfer rate (k_(et)) and 56% of the association constant (K_a) normally observed between cytochrome c and native CcO under otherwise identical conditions. Since the effective electron transfer rate constant is the product of k_(et), and K_a under nonsaturation conditions, the overall electron-transfer rate has been curtailed by over a factor of 2. Similar observations have been noted with the native CcO in the presence of 3 mM ATP. In contrast, the redox potential of neither CU_A nor cytochrome a was altered upon 8-azido-ATP modification or in the presence of 3 mM ATP. Also, no gross structural changes at either the CU_A or the cytochrome a site were noted, as evidenced by a lack of any spectral perturbations in the EPR signals from both of these centers. We conclude that ATP modulates the electron transfer from cytochrome c to CcO by interacting with the CcO and altering allosterically the docking. In this manner, ATP can affect the branching of the electron input from ferrocytochrome c to cytochrome a and CU_A.

Item Type:Article
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Chan, Sunney I.0000-0002-5348-2723
Additional Information:© 1995 American Chemical Society. Published in print 16 May 1995. This work was supported by NIH Grant GM 22432 from the National Institute of General Medical Sciences, U.S. Public Health Service. Contribution No. 9015 We are grateful to Prof. Gordon Tollin of Department of Biochemistry, University of Arizona, Tucson, for a gift of 5-DRF. We also thank Dr. Jay Winkler, manager of the Laser Facility at the Beckman Institute of the California Institute of Technology, for advice and technical assistance in the laser experiments.
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NIHGM 22432
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Caltech Division of Chemistry and Chemical Engineering9015
Issue or Number:19
Record Number:CaltechAUTHORS:20180205-074945747
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Official Citation:Electron transfer from cytochrome c to 8-azido-ATP-modified cytochrome c oxidase Jian Lin, Shuguang Wu, and Sunney I. Chan Biochemistry 1995 34 (19), 6335-6343 DOI: 10.1021/bi00019a011
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84663
Deposited By: Ruth Sustaita
Deposited On:05 Feb 2018 23:45
Last Modified:15 Nov 2021 20:21

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