Portal de Periódicos da CAPES

Mitochondrial Preprotein Translocase of Trypanosomatids Has a Bacterial Origin

2011; Elsevier BV; Volume: 21; Issue: 20 Linguagem: Inglês

10.1016/j.cub.2011.08.060

1879-0445

Mascha Pusnik, Oliver Schmidt, Andrew Perry, Silke Oeljeklaus, Moritz Niemann, Bettina Warscheid, Trevor Lithgow, Chris Meisinger, André Schneider,

Lysosomal Storage Disorders Research

Mitochondria are found in all eukaryotic cells and derive from a bacterial endosymbiont [1Gray M.W. Burger G. Lang B.F. The origin and early evolution of mitochondria.Genome Biol. 2001; 2: 1018.1-1018.5Crossref Google Scholar, 2Embley T.M. Martin W. Eukaryotic evolution, changes and challenges.Nature. 2006; 440: 623-630Crossref PubMed Scopus (661) Google Scholar]. The evolution of a protein import system was a prerequisite for the conversion of the endosymbiont into a true organelle. Tom40, the essential component of the protein translocase of the outer membrane, is conserved in mitochondria of almost all eukaryotes but lacks bacterial orthologs [3Hewitt V. Alcock F. Lithgow T. Minor modifications and major adaptations: the evolution of molecular machines driving mitochondrial protein import.Biochim. Biophys. Acta. 2011; 1808: 947-954Crossref PubMed Scopus (50) Google Scholar, 4Lithgow T. Schneider A. Evolution of macromolecular import pathways in mitochondria, hydrogenosomes and mitosomes.Philos. Trans. R. Soc. Lond. B Biol. Sci. 2010; 365: 799-817Crossref PubMed Scopus (79) Google Scholar, 5Dolezal P. Likic V. Tachezy J. Lithgow T. Evolution of the molecular machines for protein import into mitochondria.Science. 2006; 313: 314-318Crossref PubMed Scopus (416) Google Scholar, 6Hill K. Model K. Ryan M.T. Dietmeier K. Martin F. Wagner R. Pfanner N. Tom40 forms the hydrophilic channel of the mitochondrial import pore for preproteins [see comment].Nature. 1998; 395: 516-521Crossref PubMed Scopus (389) Google Scholar]. It serves as the gateway through which all mitochondrial proteins are imported. The parasitic protozoa Trypanosoma brucei and its relatives do not have a Tom40-like protein, which raises the question of how proteins are imported by their mitochondria [7Pusnik M. Charrière F. Mäser P. Waller R.F. Dagley M.J. Lithgow T. Schneider A. The single mitochondrial porin of Trypanosoma brucei is the main metabolite transporter in the outer mitochondrial membrane.Mol. Biol. Evol. 2009; 26: 671-680Crossref PubMed Scopus (82) Google Scholar, 8Schneider A. Bursać D. Lithgow T. The direct route: a simplified pathway for protein import into the mitochondrion of trypanosomes.Trends Cell Biol. 2008; 18: 12-18Abstract Full Text Full Text PDF PubMed Scopus (70) Google Scholar]. Using a combination of bioinformatics and in vivo and in vitro studies, we have discovered that T. brucei likely employs a different import channel, termed ATOM (archaic translocase of the outer mitochondrial membrane). ATOM mediates the import of nuclear-encoded proteins into mitochondria and is essential for viability of trypanosomes. It is not related to Tom40 but is instead an ortholog of a subgroup of the Omp85 protein superfamily that is involved in membrane translocation and insertion of bacterial outer membrane proteins [9Gentle I.E. Burri L. Lithgow T. Molecular architecture and function of the Omp85 family of proteins.Mol. Microbiol. 2005; 58: 1216-1225Crossref PubMed Scopus (187) Google Scholar]. This suggests that the protein import channel in trypanosomes is a relic of an archaic protein transport system that was operational in the ancestor of all eukaryotes.