Characterization of the exchangeable protons in the immediate vicinity of the semiquinone radical at the QH site of the cytochrome bo3 from Escherichia coli.

The Journal of Biological Chemistry
Lai Lai YapSergei A Dikanov

Abstract

The cytochrome bo3 ubiquinol oxidase from Escherichia coli resides in the bacterial cytoplasmic membrane and catalyzes the two-electron oxidation of ubiquinol-8 and four-electron reduction of O2 to water. The one-electron reduced semiquinone forms transiently during the reaction, and the enzyme has been demonstrated to stabilize the semiquinone. Two-dimensional electron spin echo envelope modulation has been applied to explore the exchangeable protons involved in hydrogen bonding to the semiquinone by substitution of 1H2O by 2H2O. Three exchangeable protons possessing different isotropic and anisotropic hyperfine couplings were identified. The strength of the hyperfine interaction with one proton suggests a significant covalent O-H binding of carbonyl oxygen O1 that is a characteristic of a neutral radical, an assignment that is also supported by the unusually large hyperfine coupling to the methyl protons. The second proton with a large anisotropic coupling also forms a strong hydrogen bond with a carbonyl oxygen. This second hydrogen bond, which has a significant out-of-plane character, is from an NH2 or NH nitrogen, probably from an arginine (Arg-71) known to be in the quinone binding site. Assignment of the third exchangeab...Continue Reading

References

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Citations

Aug 3, 2010·Journal of the American Chemical Society·Erik MartinSergei A Dikanov
Sep 14, 2011·The Journal of Physical Chemistry. a·Rimma I SamoilovaSergei A Dikanov
Dec 23, 2008·The Journal of Physical Chemistry. a·Derrick R J KollingSergei A Dikanov
Jul 10, 2007·The Journal of Biological Chemistry·Sergei A DikanovAntony R Crofts
Apr 27, 2010·Biochimica Et Biophysica Acta·Lai Lai YapRobert B Gennis
Jan 26, 2010·Biochimica Et Biophysica Acta·Sophie A WeissLars J C Jeuken
May 26, 2017·Journal of the American Chemical Society·Sylvia K ChoiRobert B Gennis
Jul 21, 2007·Angewandte Chemie·Riccardo AmoratiGian Franco Pedulli
Sep 7, 2013·Chembiochem : a European Journal of Chemical Biology·Preethi R VennamMichael K Bowman
Nov 12, 2009·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·Scott E Boesch, Ralph A Wheeler
Nov 7, 2009·The Journal of Biological Chemistry·Stéphane GrimaldiBruno Guigliarelli
Nov 29, 2011·Organic & Biomolecular Chemistry·Riccardo Amorati, Gian Franco Pedulli
Jan 1, 2020·Proceedings of the National Academy of Sciences of the United States of America·Jingjing XuJiapeng Zhu
Feb 27, 2017·Biochimica Et Biophysica Acta. Bioenergetics·Sylvia K ChoiRobert B Gennis
Aug 1, 2009·EcoSal Plus·Vitaliy B Borisov, Michael I Verkhovsky
Jan 7, 2016·EcoSal Plus·Vitaliy B Borisov, Michael I Verkhovsky

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