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Conformation-driven and semiquinone-gated proton-pump mechanism in the NADH-ubiquinone oxidoreductase (complex I).
Ohnishi, Tomoko; Salerno, John C.
Afiliação
  • Ohnishi T; Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA. ohnishi@mail.med.upenn.edu
FEBS Lett ; 579(21): 4555-61, 2005 Aug 29.
Article em En | MEDLINE | ID: mdl-16098512
ABSTRACT
A novel mechanism for proton/electron transfer is proposed for NADH-quinone oxidoreductase (complex I) based on the following

findings:

(1) EPR signals of the protein-bound fast-relaxing semiquinone anion radicals (abbreviated as Q(Nf)-) are observable only in the presence of proton-transmembrane electrochemical potential; (2) Iron-sulfur cluster N2 and Q(Nf)- are directly spin-coupled; and (3) The projection of the interspin vector extends only 5A along the membrane normal [Yano, T., Dunham, W.R. and Ohnishi, T. (2005) Biochemistry, 44, 1744-1754]. We propose that the proton pump is operated by redox-driven conformational changes of the quinone binding protein. In the input state, semiquinone is reduced to quinol, acquiring two protons from the N (matrix) side of the mitochondrial inner membrane and an electron from the low potential (NADH) side of the respiratory chain. A conformational change brings the protons into position for release at the P (inter-membrane space) side of the membrane via a proton-well. Concomitantly, an electron is donated to the quinone pool at the high potential side of the coupling site. The system then returns to the original state to repeat the cycle. This hypothesis provides a useful frame work for further investigation of the mechanism of proton translocation in complex I.
Assuntos
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Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Conformação Proteica / Benzoquinonas / Bombas de Próton / Complexo I de Transporte de Elétrons Tipo de estudo: Prognostic_studies Idioma: En Ano de publicação: 2005 Tipo de documento: Article
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Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Conformação Proteica / Benzoquinonas / Bombas de Próton / Complexo I de Transporte de Elétrons Tipo de estudo: Prognostic_studies Idioma: En Ano de publicação: 2005 Tipo de documento: Article