Active remodelling of the TIM23 complex during translocation of preproteins into mitochondria

EMBO J. 2008 May 21;27(10):1469-80. doi: 10.1038/emboj.2008.79. Epub 2008 Apr 17.


The TIM23 (translocase of the mitochondrial inner membrane) complex mediates translocation of preproteins across and their insertion into the mitochondrial inner membrane. How the translocase mediates sorting of preproteins into the two different subcompartments is poorly understood. In particular, it is not clear whether association of two operationally defined parts of the translocase, the membrane-integrated part and the import motor, depends on the activity state of the translocase. We established conditions to in vivo trap the TIM23 complex in different translocation modes. Membrane-integrated part of the complex and import motor were always found in one complex irrespective of whether an arrested preprotein was present or not. Instead, we detected different conformations of the complex in response to the presence and, importantly, the type of preprotein being translocated. Two non-essential subunits of the complex, Tim21 and Pam17, modulate its activity in an antagonistic manner. Our data demonstrate that the TIM23 complex acts as a single structural and functional entity that is actively remodelled to sort preproteins into different mitochondrial subcompartments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Membrane Proteins / metabolism
  • Membrane Transport Proteins / metabolism*
  • Mitochondria / metabolism*
  • Mitochondrial Membrane Transport Proteins
  • Protein Conformation
  • Protein Transport
  • Repressor Proteins / metabolism
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / metabolism*


  • Membrane Proteins
  • Membrane Transport Proteins
  • Mitochondrial Membrane Transport Proteins
  • Pam17 protein, S cerevisiae
  • Repressor Proteins
  • Saccharomyces cerevisiae Proteins
  • TIM17 protein, S cerevisiae
  • TIM23 protein, S cerevisiae
  • Tim21 protein, S cerevisiae