Evolution of respiratory complex I: "supernumerary" subunits are present in the alpha-proteobacterial enzyme.

TitleEvolution of respiratory complex I: "supernumerary" subunits are present in the alpha-proteobacterial enzyme.
Publication TypeJournal Article
Year of Publication2011
AuthorsYip, C-ying, Harbour, ME, Jayawardena, K, Fearnley, IM, Sazanov, LA
JournalJ Biol Chem
Date Published2011 Feb 18
KeywordsAnimals, Bacterial Proteins, Catalytic Domain, Cattle, Electron Transport Complex I, Evolution, Molecular, Mitochondrial Proteins, Paracoccus denitrificans

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.

Alternate JournalJ. Biol. Chem.
Citation Key10.1074/jbc.M110.194993
PubMed ID21115482
PubMed Central IDPMC3037614
Grant ListMC_U105674180 / / Medical Research Council / United Kingdom