--- res: bibo_abstract: - 'Modern α-proteobacteria are thought to be closely related to the ancient symbiont of eukaryotes, an ancestor of mitochondria. Respiratory complex I from α-proteobacteria and mitochondria is well conserved at the level of the 14 "core" subunits, consistent with that notion. Mitochondrial complex I contains the core subunits, present in all species, and up to 31 "supernumerary" subunits, generally thought to have originated only within eukaryotic lineages. However, the full protein composition of an α-proteobacterial complex I has not been established previously. Here, we report the first purification and characterization of complex I from the α-proteobacterium Paracoccus denitrificans. Single particle electron microscopy shows that the complex has a well defined L-shape. Unexpectedly, in addition to the 14 core subunits, the enzyme also contains homologues of three supernumerary mitochondrial subunits as follows: B17.2, AQDQ/18, and 13 kDa (bovine nomenclature). This finding suggests that evolution of complex I via addition of supernumerary or "accessory" subunits started before the original endosymbiotic event that led to the creation of the eukaryotic cell. It also provides further confirmation that α-proteobacteria are the closest extant relatives of mitochondria.@eng' bibo_authorlist: - foaf_Person: foaf_givenName: Chui foaf_name: Yip, Chui Y foaf_surname: Yip - foaf_Person: foaf_givenName: Michael foaf_name: Harbour, Michael E foaf_surname: Harbour - foaf_Person: foaf_givenName: Kamburapola foaf_name: Jayawardena, Kamburapola G foaf_surname: Jayawardena - foaf_Person: foaf_givenName: Ian foaf_name: Fearnley, Ian M foaf_surname: Fearnley - foaf_Person: foaf_givenName: Leonid A foaf_name: Leonid Sazanov foaf_surname: Sazanov foaf_workInfoHomepage: http://www.librecat.org/personId=338D39FE-F248-11E8-B48F-1D18A9856A87 orcid: 0000-0002-0977-7989 bibo_doi: 10.1074/jbc.M110.194993 bibo_issue: '7' bibo_volume: 286 dct_date: 2011^xs_gYear dct_publisher: American Society for Biochemistry and Molecular Biology@ dct_title: Evolution of respiratory complex I "Supernumerary" subunits are present in the α-proteobacterial enzyme@ ...