title: Assembly of the Escherichia coli NADH:ubiquinone oxidoreductase (complex I).
abstract: The proton-pumping NADH:ubiquinone oxidoreductase is the first of the respiratory chain complexes in many bacteria and the mitochondria of most eukaryotes. In general, the bacterial complex consists of 14 different subunits. In addition to the homologues of these subunits, the mitochondrial complex contains approximately 31 additional proteins. While it was shown that the mitochondrial complex is assembled from distinct intermediates, nothing is known about the assembly of the bacterial complex. We used Escherichia coli mutants, in which the nuo-genes coding the subunits of complex I were individually disrupted by an insertion of a resistance cartridge to determine whether they are required for the assembly of a functional complex I. No complex I-mediated enzyme activity was detectable in the mutant membranes and it was not possible to extract a structurally intact complex I from the mutant membranes. However, the subunits and the cofactors of the soluble NADH dehydrogenase fragment of the complex were detected in the cytoplasm of some of the nuo-mutants. It is discussed whether this fragment represents an assembly intermediate. In addition, a membrane-bound fragment exhibiting NADH/ferricyanide oxidoreductase activity and containing the iron-sulfur cluster N2 was detected in one mutant.
authors.affiliation: Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schneider
authors.forename: Thomas
authors.initials: T
authors.lastname: Pohl
authors.forename: Julia
authors.initials: J
authors.lastname: Walter
authors.forename: Katerina
authors.initials: K
authors.lastname: Dörner
authors.forename: Markus
authors.initials: M
authors.lastname: Kohlstädt
authors.forename: Annette
authors.initials: A
authors.lastname: Berger
authors.forename: Volker
authors.initials: V
authors.lastname: Spehr
authors.forename: Thorsten
authors.initials: T
authors.lastname: Friedrich
mesh_terms: D002499:Centrifugation, Density Gradient; D003593:Cytoplasm / Q000201:enzymology; D004578:Electron Spin Resonance Spectroscopy; D042967:Electron Transport Complex I / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D005798:Genes, Bacterial; D007700:Kinetics; D009154:Mutation
chemical_list: D029968:Escherichia coli Proteins; D042967:Electron Transport Complex I