Locking loop movement in the ubiquinone pocket of complex I disengages the proton pumps
Por:
Cabrera-Orefice A., Yoga E.G., Wirth C., Siegmund K., Zwicker K., Guerrero-Castillo S., Zickermann V., Hunte C., Brandt U.
Publicada:
1 ene 2018
Resumen:
Complex I (proton-pumping NADH:ubiquinone oxidoreductase) is the largest enzyme of the mitochondrial respiratory chain and a significant source of reactive oxygen species (ROS). We hypothesized that during energy conversion by complex I, electron transfer onto ubiquinone triggers the concerted rearrangement of three protein loops of subunits ND1, ND3, and 49-kDa thereby generating the power-stoke driving proton pumping. Here we show that fixing loop TMH1-2ND3 to the nearby subunit PSST via a disulfide bridge introduced by site-directed mutagenesis reversibly disengages proton pumping without impairing ubiquinone reduction, inhibitor binding or the Active/Deactive transition. The X-ray structure of mutant complex I indicates that the disulfide bridge immobilizes but does not displace the tip of loop TMH1-2ND3. We conclude that movement of loop TMH1-2ND3 located at the ubiquinone-binding pocket is required to drive proton pumping corroborating one of the central predictions of our model for the mechanism of energy conversion by complex I proposed earlier. © 2018, The Author(s).
Filiaciones:
Radboud Institute for Molecular Life Sciences, Department of Pediatrics, Radboud University Medical Center, Geert Grooteplein-Zuid 10, Nijmegen, 6525, GA, Netherlands
Cluster of Excellence Macromolecular Complexes, Goethe-University, Max von Laue Str. 9, Frankfurt am Main, 60438, Germany
Institute of Biochemistry II, Medical School, Goethe University, Max von Laue Str. 9, Frankfurt am Main, 60438, Germany
Centre for Biomolecular Magnetic Resonance, Institute for Biophysical Chemistry, Goethe University, Max von Laue Str. 9, Frankfurt am Main, 60438, Germany
Institute for Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, BIOSS Centre for Biological Signalling Studies, University of Freiburg, Stefan-Meier-Str. 17, Freiburg im Breisgau, 79104, Germany
Institute of Biochemistry I, Medical School, Goethe University, Theodor-Stern-Kai 7, Frankfurt am Main, 60590, Germany
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