Redox-induced activation of the proton pump in the respiratory complex I.
Complex I functions as a redox-linked proton pump in the respiratory chains of mitochondria and bacteria, driven by the reduction of quinone (Q) by NADH. Remarkably, the distance between the Q reduction site and the most distant proton channels extends nearly 200 Å. To elucidate the molecular origin of this long-range coupling, we apply a combination of large-scale molecular simulations and a site-directed mutagenesis experiment of a key residue. In hybrid quantum mechanics/molecular mechanics simulations, we observe that reduction of Q is coupled to its local protonation by the His-38/Asp-139 ion pair and Tyr-87 of subunit Nqo4. Atomistic classical molecular dynamics simulations further suggest that formation of quinol (QH2) triggers rapid dissociation of the anionic Asp-139 toward the membrane domain that couples to conformational changes in a network of conserved charged residues. Site-directed mutagenesis data confirm the importance of Asp-139; upon mutation to asparagine the Q reductase activity is inhibited by 75%. The current results, together with earlier biochemical data, suggest that the proton pumping in complex I is activated by a unique combination of electrostatic and conformational transitions.
Department of Physics, Tampere University of Technology, FI-33101 Tampere, Finland;
Vivek
V
Sharma
Helsinki Bioenergetics Group, Programme for Structural Biology and Biophysics, Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland;
Galina
G
Belevich
Department of Chemistry, Technische Universität München, D-85748 Garching, Germany;
Ana P
AP
Gamiz-Hernandez
Department of Physics, Tampere University of Technology, FI-33101 Tampere, Finland;
Tomasz
T
Róg
Department of Physics, Tampere University of Technology, FI-33101 Tampere, Finland; MEMPHYS-Center for Biomembrane Physics, Department of Physics, University of Southern Denmark, DK-5230 Odense, Denmark;
Ilpo
I
Vattulainen
Helsinki Bioenergetics Group, Programme for Structural Biology and Biophysics, Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland;
Marina L
ML
Verkhovskaya
Helsinki Bioenergetics Group, Programme for Structural Biology and Biophysics, Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland;
Mårten
M
Wikström
Department of Theoretical Biophysics, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany.
Gerhard
G
Hummer
Department of Chemistry, Technische Universität München, D-85748 Garching, Germany; ville.kaila@ch.tum.de.
Ville R I
VR
Kaila
D004579:Electron Transport; D042967:Electron Transport Complex I / Q000502:physiology*; D004926:Escherichia coli / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000502:physiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017494:Proton Pumps / Q000502:physiology; D055672:Static Electricity; D013696:Temperature; D016963:Thermus thermophilus / Q000201:enzymology; D014965:X-Rays
D008051:Lipid Bilayers; D045322:Photosynthetic Reaction Center Complex Proteins; D017494:Proton Pumps; D042967:Electron Transport Complex I
NADH-quinone oxidoreductase; QM/MM simulations; cell respiration; electron transfer; molecular dynamics simulations