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          Institute: MPI für Biophysik     Collection: Abt. Molekulare Membranbiologie     Display Documents

ID: 534553.0, MPI für Biophysik / Abt. Molekulare Membranbiologie
The high-affinity QH binding site in quinol oxidase as studied by DONUT-HYSCORE spectroscopy and density functional theory
Authors:MacMillan, Fraser; Kacprzak, Sylwia; Hellwig, Petra; Grimaldi, Stephane; Michel, Hartmut; Kaupp, Martin
Date of Publication (YYYY-MM-DD):2011
Title of Journal:Faraday Discussions
Journal Abbrev.:Faraday Discuss.
Start Page:315
End Page:344
Title of Issue:Spectroscopy, Theory and Mechanism in Bioinorganic Chemistry
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The Cytochrome bo3 ubiquinol oxidase (QOX) from Escherichia coli (E. coli) contains a redox-active quinone, the so-called ‘‘high-affinity’’ QH quinone. The location of this cofactor and its binding site has yet to be accurately determined by X-ray crystallographic studies. Based on site-directed mutagenesis studies, a putative quinone binding site in the protein has been proposed. The exact binding partner of this cofactor and also whether it is stabilised as an anionic semiquinone or as a neutral radical species is a matter of some speculation. Both Hyperfine Sub-level Correlation (HYSCORE) and Double Nuclear Coherence Transfer Spectroscopy (DONUT-HYSCORE) spectroscopy as well as density functional theory (DFT) have been applied to investigate the QH binding site in detail to resolve these issues. Use is made of site-directed variants as well as globally 15N/14N-exchanged protein. Comparison of computed and experimental 13C hyperfine tensors provides strong support for the binding of the semiquinone radical in an anionic rather than a neutral protonated form. These results are compared with the corresponding information available on other protein binding sites and/or on model systems and are discussed with regard to the location and potential function of QH in the overall mechanism of function of this family of haem copper oxidases.
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Biophysik/Abteilung Molekulare Membranbiologie
External Affiliations:Henry Wellcome Unit of Biological EPR, School of Chemistry, University of East Anglia,
Norwich, NR4 7TJ, UK;
Institut für Physikalische Chemie, Universität Freiburg, 79104 Freiburg, Germany;
Institut de Chimie, UMR 7177, Université de Strasbourg, Strasbourg, F-67000, France;
Université d’Aix-Marseille/CNRS, BIP UPR 9036, F-13402 Marseille, France;
Technische Universität Berlin, Institut für Chemie, Sekr. C7, Strasse des 17. Juni 135, 10623 Berlin, Germany
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