title: Nucleotide-induced conformational changes in the Escherichia coli NADH:ubiquinone oxidoreductase (complex I).
abstract: The energy-converting NADH:ubiquinone oxidoreductase, also known as respiratory complex I, couples the transfer of electrons from NADH to ubiquinone with the translocation of protons across the membrane. Electron microscopy revealed the two-part structure of the complex consisting of a peripheral and a membrane arm. The peripheral arm contains all known cofactors and the NADH-binding site, whereas the membrane arm has to be involved in proton translocation. Owing to this, a conformation-linked mechanism for redox-driven proton translocation is discussed. By means of electron microscopy, we show that both arms of the Escherichia coli complex I are widened after the addition of NADH but not of NADPH. NADH-induced conformational changes were also detected in solution: ATR-FTIR (attenuated total reflection Fourier-transform infrared) of the soluble NADH dehydrogenase fragment of the complex indicates protein re-arrangements induced by the addition of NADH. EPR spectroscopy of surface mutants of the complex containing a covalently bound spin label at distinct positions demonstrates NADH-dependent conformational changes in both arms of the complex.
authors.affiliation: Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Albertstrasse 21, D-79104 Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pohl
authors.forename: Daniel
authors.initials: D
authors.lastname: Schneider
authors.forename: Ruth
authors.initials: R
authors.lastname: Hielscher
authors.forename: Stefan
authors.initials: S
authors.lastname: Stolpe
authors.forename: Katerina
authors.initials: K
authors.lastname: Dörner
authors.forename: Markus
authors.initials: M
authors.lastname: Kohlstädt
authors.forename: Bettina
authors.initials: B
authors.lastname: Böttcher
authors.forename: Petra
authors.initials: P
authors.lastname: Hellwig
authors.forename: Thorsten
authors.initials: T
authors.lastname: Friedrich
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D042967:Electron Transport Complex I / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism*; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011522:Protons; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D029968:Escherichia coli Proteins; D009711:Nucleotides; D011522:Protons; D009243:NAD; D042967:Electron Transport Complex I