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      Crystal structure of the entire respiratory complex I

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          Abstract

          Complex I is the first and largest enzyme of the respiratory chain, playing a central role in cellular energy production by coupling electron transfer between NADH and ubiquinone to proton translocation. It is implicated in many common human neurodegenerative diseases. Here we report the first crystal structure of the entire, intact complex I (from T. thermophilus) at 3.3 Å resolution. The structure of the 536 kDa complex comprises 16 different subunits with 64 transmembrane helices and 9 Fe-S clusters. The core fold of subunit Nqo8 (NuoH/ND1) is, unexpectedly, similar to a half-channel of the antiporter-like subunits. Small subunits nearby form a linked second half-channel, thus completing the fourth proton translocation pathway, in addition to the channels in three antiporter-like subunits. The quinone-binding site is unusually long, narrow and enclosed. The quinone headgroup binds at the deep end of this chamber, near cluster N2. Strikingly, the chamber is linked to the fourth channel by a “funnel” of charged residues. The link continues over the entire membrane domain as a remarkable flexible central axis of charged and polar residues. It likely plays a leading role in the propagation of conformational changes, aided by coupling elements. The structure suggests that a unique, out-of-the-membrane quinone reaction chamber allows the redox energy to drive concerted long-range conformational changes in the four antiporter-like domains, resulting in translocation of four protons per cycle.

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          Author and article information

          Journal
          0410462
          6011
          Nature
          Nature
          Nature
          0028-0836
          1476-4687
          3 January 2013
          17 February 2013
          28 February 2013
          28 August 2013
          : 494
          : 7438
          : 443-448
          Affiliations
          Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, U.K.
          Author notes
          Correspondence and requests for materials should be addressed to L. S. ( sazanov@ 123456mrc-mbu.cam.ac.uk ).
          [1]

          Present address: European Bioinformatics Institute, Cambridge CB10 1SD, U.K.

          Author Contributions: R. B. purified and crystallised the intact complex; J.B. purified and crystallised the membrane domain; G.M. performed co-crystallisation and soaks with quinone analogues; all authors collected and analysed X-ray data; L. S. designed and supervised the project, analyzed data and wrote the manuscript, with contributions from all authors.

          Article
          EMS50981
          10.1038/nature11871
          3672946
          23417064
          9b16b591-0470-42a9-9276-5b629c6f8c89

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