Elucidating mechanisms in haem copper oxidases: The high-affinity Q(H) binding site in quinol oxidase as studied by DONUT-HYSCORE spectroscopy and density functional theory

Macmillan, F., Kacprzak, S., Hellwig, P., Grimaldi, S., Michel, H. and Kaupp, M. (2011) Elucidating mechanisms in haem copper oxidases: The high-affinity Q(H) binding site in quinol oxidase as studied by DONUT-HYSCORE spectroscopy and density functional theory. Faraday Discussions, 148. pp. 315-344. ISSN 1364-5498

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Abstract

The Cytochrome bo(3) ubiquinol oxidase (QOX) from Escherichia coli (E. coli) contains a redox-active quinone, the so-called "high-affinity'' Q(H) 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 N-15/(14) N-exchanged protein. Comparison of computed and experimental C-13 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.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Depositing User: Rachel Smith
Date Deposited: 18 Jul 2011 12:11
Last Modified: 21 Apr 2020 16:49
URI: https://ueaeprints.uea.ac.uk/id/eprint/33904
DOI: 10.1039/c005149g

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