Mitochondrial preprotein translocase of trypanosomatids has a bacterial origin

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

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81 Citations (Scopus)


Mitochondria are found in all eukaryotic cells and derive from a bacterial endosymbiont [1, 2]. 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 [3-6]. 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 [7, 8]. 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 [9]. 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. 

Original languageEnglish
Pages (from-to)1738-1743
Number of pages6
JournalCurrent Biology
Issue number20
Publication statusPublished - 25 Oct 2011

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