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Journal of Biochemistry Advance Access published online on January 27, 2009
Journal of Biochemistry, doi:10.1093/jb/mvp015
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© The authors 2008. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.

Effects of Replacement of Low-spin Heme b by Heme O on Escherichia coli Cytochrome bo and bd Quinol Oxidases

Tatsushi Mogi1,2,*

1Department of Biomedical Chemistry, Graduate School of Medicine, the University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033; 2ATP System Project, ERATO, JST, Nagatsuta, Midori-ku, Yokohama 226-0026, Japan

*To whom correspondence 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

Cytochrome 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 heme species in the oxidation of quinols, intramolecular electron transfer and the dioxygen reduction, we replaced b-hemes with heme O by using the heme O synthase-overproducing system, which can accumulate heme O in cytoplasmic membranes. Characterizations of spectroscopic properties of cytochrome bo and bd isolated from BL21 (DE3)/pLysS and BL21 (DE3)/pLysS/pTTQ18-cyoE after 4 hrs of the aerobic induction of heme O synthase (CyoE) showed the specific incorporation of heme O into the low-spin heme binding site in both oxidases. We found that the resultant heme 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 heme B is required at the low-spin heme site for the oxidation of quinols by cytochrome bo and bd.


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