title: A novel, enzymatically active conformation of the Escherichia coli NADH:ubiquinone oxidoreductase (complex I).
abstract: Electron microscopy has demonstrated the unusual L-shaped structure of the respiratory complex I consisting of two arms, which are arranged perpendicular to each other. We found that the Escherichia coli complex I has an additional stable conformation, with the two arms arranged side by side, resulting in a horseshoe-shaped structure. The structure of both conformations was determined by means of electron microscopy of gold thioglucose-stained single particles. They were distinguished from each other by titration of the complex with polyethylene glycol and by means of analytical ultracentrifugation. The transition between the two conformations is induced by the ionic strength of the buffer and is reversible. Only the horseshoe-shaped complex I exhibits enzyme activity in detergent solution, which is abolished by the addition of salt. Therefore, it is proposed that this structure is the native conformation of the complex in the membrane.
authors.affiliation: Structural Biology and Biocomputing Programme, European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Böttcher
authors.forename: Dierk
authors.initials: D
authors.lastname: Scheide
authors.forename: Micaela
authors.initials: M
authors.lastname: Hesterberg
authors.forename: Luitgard
authors.initials: L
authors.lastname: Nagel-Steger
authors.forename: Thorsten
authors.initials: T
authors.lastname: Friedrich
mesh_terms: D006051:Aurothioglucose; D042967:Electron Transport Complex I; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology*; D005583:Fourier Analysis; D008854:Microscopy, Electron; D008956:Models, Chemical; D008958:Models, Molecular; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry*; D009994:Osmolar Concentration; D011487:Protein Conformation
chemical_list: D006051:Aurothioglucose; D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I