8-Azido-ATP Modification of Cytochrome c: Retardation of Its Electron-Transfer Activity to Cytochrome c Oxidase
- Creators
- Lin, Jian
- Wu, Shuguang
- Lau, Wa-to
-
Chan, Sunney I.
Abstract
Horse heart cytochrome c has been modified by 8-azido-ATP and the electron-transfer activity of the modified cytochrome c's to bovine heart cytochrome c oxidase (CcO) under physiological ionic strengths has been studied by the laser flash photolysis technique with 5-deazariboflavin and EDTA as the electron donor. The intermolecular electron transfer between the redox protein partners was shown to be extremely slow. The 8-azido-ATP-modified system exhibited less than 5% of the intracomplex electron-transfer rate observed between native cytochrome c and CcO under otherwise identical conditions. The binding affinity of the modified cytochrome c was greatly reduced (3 orders of magnitude) at low ionic strengths; however, it was only slightly reduced (by a factor of 2) relative to the native protein at physiological ionic strengths. Thus, the binding affinity of the ATP-cytochrome c adducts is relatively insensitive to the ionic strength compared to the native enzyme, suggesting that a different docking conformation is assumed by the ATP-cytochrome c adducts in their interaction with the oxidase. Since the redox potential of the modified cytochrome c is close to the value of its native form, we conclude that there has been a change in the docking of the cytochrome c to CcO and the electronic coupling between heme c and CUA upon 8-azido-ATP modification.
Additional Information
© 1995 American Chemical Society. Published in print 28 February 1995. This work was supported by NIH Grant GM 22432 from the National Institute of General Medical Sciences, US. Public Health Service. Contribution no. 8955. We are grateful to Professor Gordon Tollin of the 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. Professor Carmichael Wallace kindly provided us with a copy of a manuscript summarizing the results of related studies prior to publication. Dr. Wallace also provided a number of helpful comments on the present study.Additional details
- Eprint ID
- 84665
- Resolver ID
- CaltechAUTHORS:20180205-083519723
- GM 22432
- NIH
- Created
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2018-02-05Created from EPrint's datestamp field
- Updated
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2021-11-15Created from EPrint's last_modified field
- Other Numbering System Name
- Caltech Division of Chemistry and Chemical Engineering
- Other Numbering System Identifier
- 8955