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Published March 25, 1993 | public
Journal Article

Transient electron-transfer studies on the two-subunit cytochrome c oxidase from Paracoccus denitrificans

Abstract

Intermolecular electron transfer between c-type cytochromes (equine cytochrome c_(550), P. denitrifcans c_(550), and P. denitrificans detergent solubilized membrane-associated c_(552)) and the two-subunit cytochrome c oxidase from P. denitrificans has been studied using a photoinitiated uroporphyrin/NADH reduction system. In the presence of cytochrome c oxidase, the oxidation of transiently produced soluble ferrocytochrome c_(550)'s was biphasic with a fast phase k_(obs) between 80 and 90 s^(-1). The simultaneous reduction of cytochrome a occurred with a k(obs) of 50 s^(-1), suggesting that cytochrome a is not the immediate electron acceptor for these soluble cytochromes. In contrast, the membrane-associated cytochrome c_(552) was not capable of transferring electrons to cytochrome c oxidase, either transiently or under steady-state conditions. It is concluded that the soluble and membrane-associated cytochrome c's utilize separate electron-transfer pathways into P. denitrifcans cytochrome c oxidase.

Additional Information

© 1993 American Chemical Society. Received: November 23, 1992. Contribution No. 8722 from the Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA. This work was supported by Grant GM22432 from the National Institute of General Medical Science, U.S.P.H.S. Portions described at the ASBMB/Biophysical Society Joint Meeting. FASEB J. 1992, 6, A284. We thank Siegfried M. Musser and Dr. Theodore J. DiMagno for helpful discussions and critically reviewing this manuscript. We also thank Dr. Thomas Harrold and Larry Tudor for expert assistance in the growth of P. denitrificans.

Additional details

Created:
August 20, 2023
Modified:
October 20, 2023