13800
Biochemistry 2000, 39, 13800-13809
Electrogenic Reactions of Cytochrome bd† Audrius Jasaitis,‡ Vitaliy B. Borisov,§ Nikolai P. Belevich,| Joel E. Morgan,‡ Alexander A. Konstantinov,§ and Michael I. Verkhovsky*,‡ A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State UniVersity, Moscow, Russia, Department of Biophysics, Faculty of Biology, Moscow State UniVersity, Russia, and Helsinki Bioenergetics Group, Department of Medical Chemistry, Institute of Biomedical Sciences and Biocentrum Helsinki, UniVersity of Helsinki, P.O. Box 8, FIN-00014, Helsinki, Finland ReceiVed May 23, 2000; ReVised Manuscript ReceiVed September 7, 2000
ABSTRACT: Cytochrome bd is one of the two terminal quinol oxidases in the respiratory chain of Escherichia coli. The enzyme catalyzes charge separation across the bacterial membrane during the oxidation of quinols by dioxygen but does not pump protons. In this work, the reaction of cytochrome bd with O2 and related reactions has been studied by time-resolved spectrophotometric and electrometric methods. Oxidation of the fully reduced enzyme by oxygen is accompanied by rapid generation of membrane potential (∆Ψ, negative inside the vesicles) that can be described by a two-step sequence of (i) an initial oxygen concentration-dependent, electrically silent, process (lag phase) corresponding to the formation of a ferrous oxy compound of heme d and (ii) a subsequent monoexponential electrogenic phase with a time constant
