The [FeFe] hydrogenase of Nyctotherus ovalis has a chimeric origin.
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.
Boxma
Brigitte
B
Department of Evolutionary Microbiology, Faculty of Science, Radboud University Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The Netherlands. Brigitte.Boxma@intervet.com
Ricard
Guenola
G
van Hoek
Angela H A M
AH
Severing
Edouard
E
Moon-van der Staay
Seung-Yeo
SY
van der Staay
Georg W M
GW
van Alen
Theo A
TA
de Graaf
Rob M
RM
Cremers
Geert
G
Kwantes
Michiel
M
McEwan
Neil R
NR
Newbold
C Jamie
CJ
Jouany
Jean-Pierre
JP
Michalowski
Tadeusz
T
Pristas
Peter
P
Huynen
Martijn A
MA
Hackstein
Johannes H P
JH
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
D007506:Iron-Sulfur Proteins; C118830:iron hydrogenase; D006864:Hydrogenase; D042967:Electron Transport Complex I