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Journal of Biochemistry Advance Access originally published online on January 27, 2009
Journal of Biochemistry 2009 145(5):599-607; doi:10.1093/jb/mvp015
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© The Authors 2009. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved

Effects of Replacement of Low-Spin Haem b by Haem O on Escherichia coli Cytochromes bo and bd Quinol Oxidases

Tatsushi Mogi*

Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033;and ATP System Project, ERATO, JST, Nagatsuta, Midori-ku, Yokohama 226-0026, Japan

*To whom correspondence should be addressed. Tel: +81-3-5841-8202, Fax: +81-3-5841-3444, E-mail: tmogi{at}m.u-tokyo.ac.jp

Received January 7, 2009; Accepted January 16, 2009


  Abstract

Cytochromes bo and bd are terminal ubiquinol oxidases in the aerobic respiratory chain of Escherichia coli and generate proton motive force across the membrane. To probe roles of haem species in the oxidation of quinols, intramolecular electron transfer and the dioxygen reduction, we replaced b-haems with haem O by using the haem O synthase-overproducing system, which can accumulate haem O in cytoplasmic membranes. Characterizations of spectroscopic properties of cytochromes bo and bd isolated from BL21 (DE3)/pLysS and BL21 (DE3)/pLysS/pTTQ18-cyoE after 4 h of the aerobic induction of haem O synthase (CyoE) showed the specific incorporation of haem O into the low-spin haem-binding site in both oxidases. We found that the resultant haem oo- and obd-type oxidase severely reduced the ubiquinol-1 oxidase activity due to the perturbations of the quinol oxidation site. Our observations suggest that haem B is required at the low-spin haem site for the oxidation of quinols by cytochromes bo and bd.

Key Words: bacterial terminal oxidase, CyoE, haem O synthase, low-spin haem b, quinol oxidation site

Abbreviations: HPLC, high-performance liquid chromatography; SML, sucrose monolaurate; TMPD, N,N.N',N'-tetramethyl-p-phenylenediamine; QH, the high-affinity quinine-binding site


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