title: Cysteine scanning reveals minor local rearrangements of the horizontal helix of respiratory complex I.
abstract: The NADH:ubiquinone oxidoreductase, respiratory complex I, couples electron transfer from NADH to ubiquinone with the translocation of protons across the membrane. The complex consists of a peripheral arm catalyzing the redox reaction and a membrane arm catalyzing proton translocation. The membrane arm is almost completely aligned by a 110 Å unique horizontal helix that is discussed to transmit conformational changes induced by the redox reaction in a piston-like movement to the membrane arm driving proton translocation. Here, we analyzed such a proposed movement by cysteine-scanning of the helix of the Escherichia coli complex I. The accessibility of engineered cysteine residues and the flexibility of individual positions were determined by labeling the preparations with a fluorescent marker and a spin-probe, respectively, in the oxidized and reduced states. The differences in fluorescence labeling and the rotational flexibility of the spin probe between both redox states indicate only slight conformational changes at distinct positions of the helix but not a large movement.
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Steimle
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schnick
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Burger
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Nuber
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Dorothée
authors.initials: D
authors.lastname: Krämer
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Hannah
authors.initials: H
authors.lastname: Dawitz
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Sofia
authors.initials: S
authors.lastname: Brander
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Bartlomiej
authors.initials: B
authors.lastname: Matlosz
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Jacob
authors.initials: J
authors.lastname: Schäfer
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Maurer
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Udo
authors.initials: U
authors.lastname: Glessner
authors.affiliation: Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Friedrich
mesh_terms: D003545:Cysteine; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D042967:Electron Transport Complex I / Q000737:chemistry* / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D009243:NAD / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D011522:Protons; D014451:Ubiquinone / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D011522:Protons; D009243:NAD; D014451:Ubiquinone; D009245:NADH Dehydrogenase; C479743:NuoL protein, E coli; D042967:Electron Transport Complex I; D003545:Cysteine