Locking loop movement in the ubiquinone pocket of complex I disengages the proton pumps

  • 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.
Author:Alfredo Cabrera-Orefice, Etienne Galemou Yoga, Christophe Wirth, Karin Siegmund, Klaus Zwicker, Sergio Guerrero-Castillo, Volker Zickermann, Carola Hunte, Ulrich BrandtORCiDGND
Pubmed Id:https://pubmed.ncbi.nlm.nih.gov/30374105
Parent Title (English):Nature Communications
Publisher:Nature Publishing Group UK
Place of publication:[London]
Document Type:Article
Year of Completion:2018
Date of first Publication:2018/10/29
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2018/11/13
Tag:Enzyme mechanisms; Mitochondrial proteins; X-ray crystallography
Issue:1, Art. 4500
Page Number:10
First Page:1
Last Page:10
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Institutes:Biochemie, Chemie und Pharmazie / Biochemie und Chemie
Medizin / Medizin
Exzellenzcluster / Exzellenzcluster Makromolekulare Komplexe
Dewey Decimal Classification:6 Technik, Medizin, angewandte Wissenschaften / 61 Medizin und Gesundheit / 610 Medizin und Gesundheit
Licence (German):License LogoCreative Commons - Namensnennung 4.0