Protein import into and across the mitochondrial inner membrane: role of the TIM23 and TIM22 translocons

Biochim Biophys Acta. 2002 Sep 2;1592(1):25-34. doi: 10.1016/s0167-4889(02)00261-6.


Import of nuclear-encoded mitochondrial proteins requires the action of at least two different import machines, called translocons, in the mitochondrial inner membrane (IM). The TIM23 complex mediates the translocation of proteins into the mitochondria matrix, whereas the TIM22 complex is required for the insertion of polytopic proteins into the IM. While the two translocons are distinct and composed of separate subunits, the essential reactions in each complex are carried out by homologous proteins. In addition, the core components of both the TIM23 and TIM22 translocons have been shown to form aqueous pores in the mitochondrial IM. In this review, we summarize what is known about import of proteins across the mitochondrial IM.

Publication types

  • Review

MeSH terms

  • Intracellular Membranes / metabolism*
  • Membrane Transport Proteins / metabolism*
  • Mitochondria / metabolism*
  • Mitochondrial ADP, ATP Translocases / metabolism
  • Mitochondrial Membrane Transport Proteins
  • Mitochondrial Proteins / metabolism*
  • Protein Precursors / chemistry
  • Protein Precursors / metabolism*
  • Protein Transport
  • Saccharomyces cerevisiae Proteins / metabolism*


  • Membrane Transport Proteins
  • Mitochondrial Membrane Transport Proteins
  • Mitochondrial Proteins
  • PET9 protein, S cerevisiae
  • Protein Precursors
  • Saccharomyces cerevisiae Proteins
  • TIM22 protein, S cerevisiae
  • TIM23 protein, S cerevisiae
  • Mitochondrial ADP, ATP Translocases