Terminal Electron–Proton Transfer Dynamics in the Quinone Reduction of Respiratory Complex I

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Gamiz-Hernandez , A P , Jussupow , A , Johansson , M P & Kaila , V 2017 , ' Terminal Electron–Proton Transfer Dynamics in the Quinone Reduction of Respiratory Complex I ' , Journal of the American Chemical Society , vol. 139 , no. 45 , pp. 16282-16288 . https://doi.org/10.1021/jacs.7b08486 , https://doi.org/10.1021/jacs.7b08486

Title: Terminal Electron–Proton Transfer Dynamics in the Quinone Reduction of Respiratory Complex I
Author: Gamiz-Hernandez, Ana P.; Jussupow, Alexander; Johansson, Mikael Peter; Kaila, Ville
Contributor: University of Helsinki, Department of Chemistry
Date: 2017
Language: eng
Number of pages: 7
Belongs to series: Journal of the American Chemical Society
ISSN: 0002-7863
URI: http://hdl.handle.net/10138/301186
Abstract: Complex I functions as a redox-driven proton pump in aerobic respiratory chains. By reducing quinone (Q), complex I employs the free energy released in the process to thermodynamically drive proton pumping across its membrane domain. The initial Q reduction step plays a central role in activating the proton pumping machinery. In order to probe the energetics, dynamics, and molecular mechanism for the proton-coupled electron transfer process linked to the Q reduction, we employ here multiscale quantum and classical molecular simulations. We identify that both ubiquinone (UQ) and menaquinone (MQ) can form stacking and hydrogen-bonded interactions with the conserved Q binding-site residue His-38 and that conformational changes between these binding modes modulate the Q redox potentials and the rate of electron transfer (eT) from the terminal N2 iron-sulfur center. We further observe that, while the transient formation of semiquinone is not proton-coupled, the second eT process couples semiconcerted proton uptake from conserved tyrosine (Tyr-87) and histidine (His-38) residues within the active site. Our calculations indicate that both UQ and MQ have low redox potentials around -260 and -230 mV, respectively, in the Q-binding site, respectively, suggesting that release of the Q toward the membrane is coupled to an energy transduction step that could thermodynamically drive proton pumping in complex I.
Subject: 116 Chemical sciences
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