The mitochondrial import machinery: preprotein-conducting channels with binding sites for presequences

Biochim Biophys Acta. 2002 Sep 2;1592(1):15-24. doi: 10.1016/s0167-4889(02)00260-4.


Mitochondrial preproteins with amino-terminal presequences must cross two membranes to reach the matrix of the organelle. Both outer and inner membranes contain hydrophilic high-conductance channels that are responsible for selective translocation of preproteins. The channels are embedded in dynamic protein complexes, the TOM complex of the outer membrane and the TIM23 complex of the inner membrane. Both channel-forming proteins, Tom40 and Tim23, carry specific binding sites for presequences, but differ in their pore size and response to a membrane potential. Studies with the TOM machinery show that other subunits of the translocase complex also provide specific binding sites for preproteins, modulate the channel activity and are critical for assembly of the channel.

Publication types

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

MeSH terms

  • Binding Sites
  • Carrier Proteins / chemistry
  • Carrier Proteins / metabolism
  • Intracellular Membranes / chemistry
  • Intracellular Membranes / metabolism*
  • Membrane Potentials
  • Membrane Transport Proteins / chemistry
  • Membrane Transport Proteins / metabolism
  • Mitochondria / metabolism*
  • Mitochondrial Membrane Transport Proteins / metabolism*
  • Protein Phosphatase 1
  • Protein Precursors / metabolism*
  • Protein Transport
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism


  • Carrier Proteins
  • Membrane Transport Proteins
  • Mitochondrial Membrane Transport Proteins
  • Protein Precursors
  • Saccharomyces cerevisiae Proteins
  • TIM23 protein, S cerevisiae
  • Tom40 protein, S cerevisiae
  • GIP1 protein, S cerevisiae
  • Protein Phosphatase 1