title: Role of subunit NuoL for proton translocation by respiratory complex I.
abstract: The NADH:ubiquinone oxidoreductase, respiratory complex I, couples the transfer of electrons from NADH to ubiquinone with a translocation of protons across the membrane. The complex consists of a peripheral arm catalyzing the electron transfer reaction and a membrane arm involved in proton translocation. The recently published X-ray structures of the complex revealed the presence of a unique 110 Å "horizontal" helix aligning the membrane arm. On the basis of this finding, it was proposed that the energy released by the redox reaction is transmitted to the membrane arm via a conformational change in the horizontal helix. The helix corresponds to the C-terminal part of the most distal subunit NuoL. To investigate its role in proton translocation, we characterized the electron transfer and proton translocation activity of complex I variants lacking either NuoL or parts of the C-terminal domain. Our data suggest that the H+/2e- stoichiometry of the ΔNuoL variant is 2, indicating a different stoichiometry for proton translocation as proposed from structural data. In addition, the same H+/e- stoichiometry is obtained with the variant lacking the C-terminal transmembraneous helix of NuoL, indicating its role in energy transmission.
authors.affiliation: Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Albertstrasse 21, 79104 Freiburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Steimle
authors.forename: Csaba
authors.initials: C
authors.lastname: Bajzath
authors.forename: Katerina
authors.initials: K
authors.lastname: Dörner
authors.forename: Marius
authors.initials: M
authors.lastname: Schulte
authors.forename: Vinzenz
authors.initials: V
authors.lastname: Bothe
authors.forename: Thorsten
authors.initials: T
authors.lastname: Friedrich
mesh_terms: D004579:Electron Transport; D042967:Electron Transport Complex I / Q000737:chemistry* / Q000378:metabolism; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D009245:NADH Dehydrogenase; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011522:Protons
chemical_list: D029968:Escherichia coli Proteins; D021122:Protein Subunits; D011522:Protons; D009245:NADH Dehydrogenase; C479743:NuoL protein, E coli; D042967:Electron Transport Complex I