Mitochondrial protein import in trypanosomes: Expect the unexpected

Traffic. 2017 Feb;18(2):96-109. doi: 10.1111/tra.12463. Epub 2017 Jan 17.


Mitochondria have many different functions, the most important one of which is oxidative phosphorylation. They originated from an endosymbiotic event between a bacterium and an archaeal host cell. It was the evolution of a protein import system that marked the boundary between the endosymbiotic ancestor of the mitochondrion and a true organelle that is under the control of the nucleus. In present day mitochondria more than 95% of all proteins are imported from the cytosol in a proces mediated by hetero-oligomeric protein complexes in the outer and inner mitochondrial membranes. In this review we compare mitochondrial protein import in the best studied model system yeast and the parasitic protozoan Trypanosoma brucei. The 2 organisms are phylogenetically only remotely related. Despite the fact that mitochondrial protein import has the same function in both species, only very few subunits of their import machineries are conserved. Moreover, while yeast has 2 inner membrane protein translocases, one specialized for presequence-containing and one for mitochondrial carrier proteins, T. brucei has a single inner membrane translocase only, that mediates import of both types of substrates. The evolutionary implications of these findings are discussed.

Keywords: S. cerevisiae; T. brucei; TIM complex; TOM complex; evolutionary cell biology; mitochondrial biogenesis; protein translocase.

Publication types

  • Review
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cytosol / metabolism
  • Humans
  • Membrane Transport Proteins / metabolism
  • Mitochondria / metabolism*
  • Mitochondrial Membranes / metabolism
  • Mitochondrial Proteins / metabolism*
  • Protein Transport / physiology*
  • Trypanosoma brucei brucei / metabolism*


  • Membrane Transport Proteins
  • Mitochondrial Proteins