Identifying involvement of Lys251/Asp252 pair in electron transfer and associated proton transfer at the quinone reduction site of Rhodobacter capsulatus cytochrome bc(1)

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Kuleta , P , Sarewicz , M , Postila , P , Rog , T & Osyczka , A 2016 , ' Identifying involvement of Lys251/Asp252 pair in electron transfer and associated proton transfer at the quinone reduction site of Rhodobacter capsulatus cytochrome bc(1) ' , Biochimica et Biophysica Acta. Bioenergetics , vol. 1857 , no. 10 , pp. 1661-1668 . https://doi.org/10.1016/j.bbabio.2016.07.003

Title: Identifying involvement of Lys251/Asp252 pair in electron transfer and associated proton transfer at the quinone reduction site of Rhodobacter capsulatus cytochrome bc(1)
Author: Kuleta, Patryk; Sarewicz, Marcin; Postila, Pekka; Rog, Tomasz; Osyczka, Artur
Contributor: University of Helsinki, Department of Physics
Date: 2016-10
Language: eng
Number of pages: 8
Belongs to series: Biochimica et Biophysica Acta. Bioenergetics
ISSN: 0005-2728
URI: http://hdl.handle.net/10138/224238
Abstract: Describing dynamics of proton transfers in proteins is challenging, but crucial for understanding processes which use them for biological functions. In cytochrome bc(1), one of the key enzymes of respiration or photosynthesis, proton transfers engage in oxidation of quinol (QH(2)) and reduction of quinone (Q) taking place at two distinct catalytic sites. Here we evaluated by site-directed mutagenesis the contribution of Lys251/Asp252 pair (bacterial numbering) in electron transfers and associated with it proton uptake to the quinone reduction site (Q(i) site). We showed that the absence of protonable group at position 251 or 252 significantly changes the equilibrium levels of electronic reactions including the Q(i)-site mediated oxidation of heme b(H), reverse reduction of heme b(H) by quinol and heme b(H)/Q(i) semiquinone equilibrium. This implicates the role of H-bonding network in binding of quinone/semiquinone and defining thermodynamic properties of Q/SQ/QH(2) triad. The Lys251/Asp252 proton path is disabled only when both protonable groups are removed. With just one protonable residue from this pair, the entrance of protons to the catalytic site is sustained, albeit at lower rates, indicating that protons can travel through parallel routes, possibly involving water molecules. This shows that proton paths display engineering tolerance for change as long as all the elements available for functional cooperation secure efficient proton delivery to the catalytic site. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license.
Subject: Cytochrome bc(1)
Mitochondrial complex III
Electron transfer
Proton transfer
Quinone
Q-CYCLE
RIESKE CLUSTER
HYDROGEN-BONDS
AMINO-ACID
COMPLEX
SPHAEROIDES
SEMIQUINONE
UBIQUINOL
PROTEIN
OXIDOREDUCTASE
1182 Biochemistry, cell and molecular biology
114 Physical sciences
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