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A new hypothesis on the simultaneous direct and indirect proton pump mechanisms in NADH‐quinone oxidoreductase (complex I)
Author(s) -
Ohnishi Tomoko,
Nakamaru-Ogiso Eiko,
Ohnishi S. Tsuyoshi
Publication year - 2010
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2010.08.039
Subject(s) - antiporters , proton , protein subunit , mutant , oxidoreductase , quinone , chemistry , proton pump , stereochemistry , crystallography , biochemistry , physics , enzyme , atpase , antiporter , quantum mechanics , membrane , gene
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 − .