Protein-cofactor interactions and EPR parameters for the Q(H) quinone binding site of quinol oxidase. A density functional study

Journal of the American Chemical Society
Sylwia KacprzakF MacMillan

Abstract

Recent multifrequency EPR studies of the "high-affinity" quinone binding site of quinol oxidase (Q(H) site) have suggested a very asymmetric hydrogen-bonding environment for the semiquinone radical anion state. Single-sided hydrogen bonding to the O1 carbonyl position was one of the proposals, which contrasts with some previous experimental indications. Here density functional calculations of the EPR parameters (g-tensors, 13C, 1H, and 17O hyperfine tensors) for a wide variety of supermolecular model complexes have been used to provide insight into the detailed relations among structure, environment, and EPR parameters of ubisemiquinone radical anions. A single-sided binding model is not able to account for the experimentally observed low g(x) component of the g-tensor or for the observed magnitude of the asymmetry of the 13C carbonyl HFC tensors. Based on the detailed comparison between computation and experiment, a model with two hydrogen bonds to O1 and one hydrogen bond to O4 is suggested for the Q(H) site, but a model with one more hydrogen bond on each side cannot be excluded. Several general conclusions on the interrelations between EPR parameters and hydrogen bond patterns of ubisemiquinones in proteins are provided.

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Citations

Feb 9, 2007·Physical Chemistry Chemical Physics : PCCP·Agnieszka RogowskaBenoît Champagne
Jul 7, 2017·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·Maryam Seif EddineStéphane Grimaldi
Nov 24, 2006·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·James R Asher, Martin Kaupp
Nov 12, 2009·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·Scott E Boesch, Ralph A Wheeler
Feb 27, 2017·Biochimica Et Biophysica Acta. Bioenergetics·Sylvia K ChoiRobert B Gennis
Apr 4, 2007·Journal of the American Chemical Society·T Robert Wu, J Michael Chong
Jan 26, 2007·The Journal of Physical Chemistry. B·Sylwia KacprzakMartin Kaupp

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