The location of NuoL and NuoM subunits in the membrane domain of the Escherichia coli complex I: implications for the mechanism of proton pumping.

TitleThe location of NuoL and NuoM subunits in the membrane domain of the Escherichia coli complex I: implications for the mechanism of proton pumping.
Publication TypeJournal Article
Year of Publication2003
AuthorsHolt, PJ, Morgan, DJ, Sazanov, LA
JournalJ Biol Chem
Volume278
Issue44
Pagination43114-20
Date Published2003 Oct 31
ISSN0021-9258
KeywordsCell Membrane, Chromatography, Gel, Detergents, Electron Transport Complex I, Electrophoresis, Polyacrylamide Gel, Escherichia coli, Escherichia coli Proteins, Models, Biological, NADH Dehydrogenase, Octoxynol, Oxidation-Reduction, Phosphorylcholine, Protein Conformation, Protein Structure, Tertiary, Protons
Abstract

The molecular organization of bacterial NADH: ubiquinone oxidoreductase (complex I or NDH-1) is not established, apart from a rough separation into dehydrogenase, connecting and membrane domains. In this work, complex I was purified from Escherichia coli and fragmented by replacing dodecylmaltoside with other detergents. Exchange into decyl maltoside led to the removal of the hydrophobic subunit NuoL from the otherwise intact complex. Diheptanoyl phosphocholine led to the loss of NuoL and NuoM subunits, whereas other subunits remained in the complex. The presence of N,N-dimethyldodecylamine N-oxide or Triton X-100 led to further disruption of the membrane domain into fragments containing NuoL/M/N, NuoA/K/N, and NuoH/J subunits. Among the hydrophilic subunits, NuoCD was most readily dissociated from the complex, whereas NuoB was partially dissociated from the peripheral arm assembly in N,N-dimethyldodecylamine N-oxide. A model of subunit arrangement in bacterial complex I based on these data is proposed. Subunits NuoL and NuoM, which are homologous to antiporters and are implicated in proton pumping, are located at the distal end of the membrane arm, spatially separated from the redox centers of the peripheral arm. This is consistent with proposals that the mechanism of proton pumping by complex I is likely to involve long range conformational changes.

DOI10.1074/jbc.M308247200
Alternate JournalJ. Biol. Chem.
Citation Key10.1074/jbc.M308247200
PubMed ID12923180