title: The [FeFe] hydrogenase of Nyctotherus ovalis has a chimeric origin.
abstract: BACKGROUND
  The hydrogenosomes of the anaerobic ciliate Nyctotherus ovalis show how mitochondria can evolve into hydrogenosomes because they possess a mitochondrial genome and parts of an electron-transport chain on the one hand, and a hydrogenase on the other hand. The hydrogenase permits direct reoxidation of NADH because it consists of a [FeFe] hydrogenase module that is fused to two modules, which are homologous to the 24 kDa and the 51 kDa subunits of a mitochondrial complex I.
  
  
  RESULTS
  The [FeFe] hydrogenase belongs to a clade of hydrogenases that are different from well-known eukaryotic hydrogenases. The 24 kDa and the 51 kDa modules are most closely related to homologous modules that function in bacterial [NiFe] hydrogenases. Paralogous, mitochondrial 24 kDa and 51 kDa modules function in the mitochondrial complex I in N. ovalis. The different hydrogenase modules have been fused to form a polyprotein that is targeted into the hydrogenosome.
  
  
  CONCLUSIONS
  The hydrogenase and their associated modules have most likely been acquired by independent lateral gene transfer from different sources. This scenario for a concerted lateral gene transfer is in agreement with the evolution of the hydrogenosome from a genuine ciliate mitochondrion by evolutionary tinkering.
authors.affiliation: Department of Evolutionary Microbiology, Faculty of Science, Radboud University Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The Netherlands. Brigitte.Boxma@intervet.com
authors.forename: Brigitte
authors.initials: B
authors.lastname: Boxma
authors.forename: Guenola
authors.initials: G
authors.lastname: Ricard
authors.forename: Angela H A M
authors.initials: AH
authors.lastname: van Hoek
authors.forename: Edouard
authors.initials: E
authors.lastname: Severing
authors.forename: Seung-Yeo
authors.initials: SY
authors.lastname: Moon-van der Staay
authors.forename: Georg W M
authors.initials: GW
authors.lastname: van der Staay
authors.forename: Theo A
authors.initials: TA
authors.lastname: van Alen
authors.forename: Rob M
authors.initials: RM
authors.lastname: de Graaf
authors.forename: Geert
authors.initials: G
authors.lastname: Cremers
authors.forename: Michiel
authors.initials: M
authors.lastname: Kwantes
authors.forename: Neil R
authors.initials: NR
authors.lastname: McEwan
authors.forename: C Jamie
authors.initials: CJ
authors.lastname: Newbold
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Jouany
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Michalowski
authors.forename: Peter
authors.initials: P
authors.lastname: Pristas
authors.forename: Martijn A
authors.initials: MA
authors.lastname: Huynen
authors.forename: Johannes H P
authors.initials: JH
authors.lastname: Hackstein
mesh_terms: D000818:Animals; D002678:Chimera / Q000235:genetics*; D016798:Ciliophora / Q000201:enzymology* / Q000235:genetics; D042967:Electron Transport Complex I / Q000235:genetics; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D054629:Genome, Mitochondrial; D018503:Genome, Protozoan; D006864:Hydrogenase / Q000235:genetics*; D007506:Iron-Sulfur Proteins / Q000235:genetics*; D010802:Phylogeny; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D007506:Iron-Sulfur Proteins; C118830:iron hydrogenase; D006864:Hydrogenase; D042967:Electron Transport Complex I