Homologue replacement in the import motor of the mitochondrial inner membrane of trypanosomes

Elife. 2020 Feb 27:9:e52560. doi: 10.7554/eLife.52560.


Many mitochondrial proteins contain N-terminal presequences that direct them to the organelle. The main driving force for their translocation across the inner membrane is provided by the presequence translocase-associated motor (PAM) which contains the J-protein Pam18. Here, we show that in the PAM of Trypanosoma brucei the function of Pam18 has been replaced by the non-orthologous euglenozoan-specific J-protein TbPam27. TbPam27 is specifically required for the import of mitochondrial presequence-containing but not for carrier proteins. Similar to yeast Pam18, TbPam27 requires an intact J-domain to function. Surprisingly, T. brucei still contains a bona fide Pam18 orthologue that, while essential for normal growth, is not involved in protein import. Thus, during evolution of kinetoplastids, Pam18 has been replaced by TbPam27. We propose that this replacement is linked to the transition from two ancestral and functionally distinct TIM complexes, found in most eukaryotes, to the single bifunctional TIM complex present in trypanosomes.

Keywords: Trypanosoma; biochemistry; chemical biology; evolution; evolutionary biology; j domain containing protein; mitochondrial protein import; presequence translocase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Mitochondria / metabolism*
  • Mitochondrial Membranes / metabolism*
  • Molecular Motor Proteins / classification
  • Molecular Motor Proteins / metabolism*
  • Phylogeny
  • Protein Binding
  • Protein Transport
  • Protozoan Proteins / classification
  • Protozoan Proteins / metabolism*
  • Trypanosoma brucei brucei / metabolism*


  • Molecular Motor Proteins
  • Protozoan Proteins