title: A new hypothesis on the simultaneous direct and indirect proton pump mechanisms in NADH-quinone oxidoreductase (complex I).
abstract: Recently, Sazanov's group reported the X-ray structure of whole complex I [Nature, 465, 441 (2010)], which presented a strong clue for a "piston-like" structure as a key element in an "indirect" proton pump. We have studied the NuoL subunit which has a high sequence similarity to Na(+)/H(+) antiporters, as do the NuoM and N subunits. We constructed 27 site-directed NuoL mutants. Our data suggest that the H(+)/e(-) stoichiometry seems to have decreased from (4H(+)/2e(-)) in the wild-type to approximately (3H(+)/2e(-)) in NuoL mutants. We propose a revised hypothesis that each of the "direct" and the "indirect" proton pumps transports 2H(+) per 2e(-).
authors.affiliation: Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6059, USA. ohnishi@mail.med.upenn.edu
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ohnishi
authors.forename: Eiko
authors.initials: E
authors.lastname: Nakamaru-Ogiso
authors.forename: S Tsuyoshi
authors.initials: ST
authors.lastname: Ohnishi
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D042967:Electron Transport Complex I / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D021122:Protein Subunits; D017494:Proton Pumps / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016963:Thermus thermophilus / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D050505:Mutant Proteins; D021122:Protein Subunits; D017494:Proton Pumps; D009245:NADH Dehydrogenase; C479743:NuoL protein, E coli; D042967:Electron Transport Complex I
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