Bioscience, Biotechnology, and Biochemistry
Online ISSN : 1347-6947
Print ISSN : 0916-8451
Biochemistry & Molecular Biology Regular Papers
Electron Transfer Processes in Subunit I Mutants of Cytochrome bo Quinol Oxidase in Escherichia coli
Kazuo KOBAYASHISeiichi TAGAWATatsushi MOGI
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2009 Volume 73 Issue 7 Pages 1599-1603

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Abstract

Cytochrome bo is a terminal quinol oxidase in the aerobic respiratory chain of Escherichia coli. Subunit I binds all four redox centers, and electrons are transferred from quinols to high-spin heme o and CuB through a bound uniquinone-8 and low-spin heme b. To explore the role of conserved charged amino acid residues, we examined the one-electron transfer processes in subunit I mutants. We found that all the mutants examined increased the electron transfer rate from the bound quinone to heme b more than 40-fold. Tyr288 and Lys362 are key residues in the K-channel for charge compensation of the heme o-CuB binuclear center with protons. The Tyr288Phe and Lys362Gln mutants showed 100-fold decreases in heme b-to-heme o electron transfer, accompanied by large increases in the redox potential of heme o. Our results indicate that electromagnetic coupling of hemes is important for facilitated heme-heme electron transfer in cytochrome bo.

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© 2009 by Japan Society for Bioscience, Biotechnology, and Agrochemistry
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