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Rapid Formation of a Semiquinone Species on Oxidation of Quinol by the Cytochrome bo 3 Oxidase from Escherichia coli

Osborne, Jeffrey P. and Musser, Sigfried M. and Schultz, Brian E. and Edmondson, Dale E. and Chan, Sunney I. and Gennis, Robert B. (1998) Rapid Formation of a Semiquinone Species on Oxidation of Quinol by the Cytochrome bo 3 Oxidase from Escherichia coli. In: Oxygen Homeostasis and Its Dynamics. Keio University Symposia for Life Science and Medicine. No.1. Springer , Tokyo, pp. 33-39. ISBN 978-4-431-68478-7.

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Many bacterial oxidases utilize dihydroquinols, such as ubiquinol or menaquinol, rather than cytochrome c as a substrate. The best-characterized ubiquinol oxidase is cytochrome bo ₃ from Escherichia coli. In this work, the initial oxidation of ubiquinol by this ubiquinol oxidase is examined. Stopped-flow UV-visible spectroscopy and rapid freeze-quench electron paramagnetic resonance (EPR) spectroscopies were used to examine the oxidation of ubiquinol-2 (UQ₂H₂) by cytochrome bo ₃ under multiple turnover conditions. The results show the rapid appearance of the semiquinone radical, coincident with the reduction of the low-spin heme b component of the enzyme. The rate of formation of the semiquinone radical is consistent with the proposition that this is a kinetically relevant intermediate in the reaction sequence. As UQ₂H₂ is depleted, the radical decays and the enzyme forms a “peroxy,” or P, complex with dioxygen. No detectable protein radical is associated with the P complex.

Item Type:Book Section
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Chan, Sunney I.0000-0002-5348-2723
Additional Information:© 1998 Springer-Verlag Tokyo.
Subject Keywords:Semiquinone; Quinol oxidase; Heme; E. coli; Peroxy state
Series Name:Keio University Symposia for Life Science and Medicine
Issue or Number:1
Record Number:CaltechAUTHORS:20200512-123507275
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103142
Deposited By: Tony Diaz
Deposited On:12 May 2020 20:54
Last Modified:16 Nov 2021 18:18

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