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Gene Review

TOM20  -  Tom20p

Saccharomyces cerevisiae S288c

Synonyms: MAS20, MOM19, Mitochondrial 20 kDa outer membrane protein, Mitochondrial import receptor subunit TOM20, Protein MAS20, ...
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High impact information on TOM20

  • We report here the NMR structure of a general import receptor, rat Tom20, in a complex with a presequence peptide derived from rat aldehyde dehydrogenase [1].
  • The single membrane anchor of Tom22 is required for a stable interaction between the core complexes, whereas its cytosolic domain serves as docking point for the peripheral receptors Tom20 and Tom70 [2].
  • Targeting of the master receptor MOM19 to mitochondria [3].
  • The deduced amino acid sequence predicts that MOM19 is anchored in the outer membrane by an NH2-terminal hydrophobic sequence, while the rest of the protein forms a hydrophilic domain exposed to the cytosol [3].
  • We have isolated the TOM core complex of Neurospora crassa by removing the receptors Tom70 and Tom20 from the isolated TOM holo complex by treatment with the detergent dodecyl maltoside [4].

Biological context of TOM20

  • Overexpression of Mom22 even suppressed the lethal phenotype of a double deletion of the two import receptors known so far (mom19 delta mom72 delta) [5].
  • Import of the purified precursor showed the characteristics of authentic mitochondrial import including use of the receptor MOM19, requirement for a membrane potential, and proteolytic processing [6].
  • Hidden Markov model searches of genome sequence data revealed novel isoforms of Tom20 in vertebrate and invertebrate animals [7].
  • Transmembrane translocation of the tRNA requires the intactness of at least two of the components of the mitochondrial import machinery of pre-proteins, MOM19 and MIM44, as well as energy of ATP hydrolysis and an electrochemical potential across the inner membrane [8].

Anatomical context of TOM20

  • Import of porin into isolated mitochondria in which the outer membrane has been opened is inhibited despite similar levels of Tom20 as in intact mitochondria [9].
  • Mas20p and Mas70p are integral proteins of the yeast mitochondrial outer membrane that appear to function as receptors for precursor proteins imported from the cytosol [10].
  • Tom20 is an outer mitochondrial membrane protein and functions as a component of the import receptor complex for the cytoplasmically synthesized mitochondrial precursor proteins [11].

Physical interactions of TOM20

  • The Mas20p and Mas70p subunits of the protein import receptor of yeast mitochondria interact via the tetratricopeptide repeat motif in Mas20p: evidence for a single hetero-oligomeric receptor [12].

Other interactions of TOM20

  • (ii) Tom20 and Tom70 are not essential for the generation of the GIP complex [13].
  • It was unknown if Mom22 directly interacts with preproteins, and two views existed about the possible functions of Mom22: a central role in transfer of preproteins from both receptors to the general insertion pore or a more limited function dependent on the presence of the receptor Mom19 [5].
  • Preproteins carrying amino-terminal signals mainly use Tom20, the general import pore (GIP) complex and the Tim23-Tim17 complex [14].
  • We report that import of the preprotein of Tim22 requires Tom20, although it uses the carrier Tim route [14].
  • Surprisingly, AAC is still associated with the receptors Tom70 and Tom20 when the function of Tim10 is impaired [15].


  1. Structural basis of presequence recognition by the mitochondrial protein import receptor Tom20. Abe, Y., Shodai, T., Muto, T., Mihara, K., Torii, H., Nishikawa, S., Endo, T., Kohda, D. Cell (2000) [Pubmed]
  2. Tom22 is a multifunctional organizer of the mitochondrial preprotein translocase. van Wilpe, S., Ryan, M.T., Hill, K., Maarse, A.C., Meisinger, C., Brix, J., Dekker, P.J., Moczko, M., Wagner, R., Meijer, M., Guiard, B., Hönlinger, A., Pfanner, N. Nature (1999) [Pubmed]
  3. Targeting of the master receptor MOM19 to mitochondria. Schneider, H., Söllner, T., Dietmeier, K., Eckerskorn, C., Lottspeich, F., Trülzsch, B., Neupert, W., Pfanner, N. Science (1991) [Pubmed]
  4. The TOM core complex: the general protein import pore of the outer membrane of mitochondria. Ahting, U., Thun, C., Hegerl, R., Typke, D., Nargang, F.E., Neupert, W., Nussberger, S. J. Cell Biol. (1999) [Pubmed]
  5. The mitochondrial receptor complex: Mom22 is essential for cell viability and directly interacts with preproteins. Hönlinger, A., Kübrich, M., Moczko, M., Gärtner, F., Mallet, L., Bussereau, F., Eckerskorn, C., Lottspeich, F., Dietmeier, K., Jacquet, M. Mol. Cell. Biol. (1995) [Pubmed]
  6. Targeting of a chemically pure preprotein to mitochondria does not require the addition of a cytosolic signal recognition factor. Becker, K., Guiard, B., Rassow, J., Söllner, T., Pfanner, N. J. Biol. Chem. (1992) [Pubmed]
  7. Patterns that define the four domains conserved in known and novel isoforms of the protein import receptor Tom20. Likić, V.A., Perry, A., Hulett, J., Derby, M., Traven, A., Waller, R.F., Keeling, P.J., Koehler, C.M., Curran, S.P., Gooley, P.R., Lithgow, T. J. Mol. Biol. (2005) [Pubmed]
  8. Mechanisms of tRNA import into yeast mitochondria: an overview. Tarassov, I.A., Martin, R.P. Biochimie (1996) [Pubmed]
  9. Biogenesis of porin of the outer mitochondrial membrane involves an import pathway via receptors and the general import pore of the TOM complex. Krimmer, T., Rapaport, D., Ryan, M.T., Meisinger, C., Kassenbrock, C.K., Blachly-Dyson, E., Forte, M., Douglas, M.G., Neupert, W., Nargang, F.E., Pfanner, N. J. Cell Biol. (2001) [Pubmed]
  10. Yeast mitochondria lacking the two import receptors Mas20p and Mas70p can efficiently and specifically import precursor proteins. Lithgow, T., Junne, T., Wachter, C., Schatz, G. J. Biol. Chem. (1994) [Pubmed]
  11. Analysis of the functional domain of the rat liver mitochondrial import receptor Tom20. Iwahashi, J., Yamazaki, S., Komiya, T., Nomura, N., Nishikawa, S., Endo, T., Mihara, K. J. Biol. Chem. (1997) [Pubmed]
  12. The Mas20p and Mas70p subunits of the protein import receptor of yeast mitochondria interact via the tetratricopeptide repeat motif in Mas20p: evidence for a single hetero-oligomeric receptor. Haucke, V., Horst, M., Schatz, G., Lithgow, T. EMBO J. (1996) [Pubmed]
  13. Preprotein translocase of the outer mitochondrial membrane: molecular dissection and assembly of the general import pore complex. Dekker, P.J., Ryan, M.T., Brix, J., Müller, H., Hönlinger, A., Pfanner, N. Mol. Cell. Biol. (1998) [Pubmed]
  14. Biogenesis of Tim proteins of the mitochondrial carrier import pathway: differential targeting mechanisms and crossing over with the main import pathway. Kurz, M., Martin, H., Rassow, J., Pfanner, N., Ryan, M.T. Mol. Biol. Cell (1999) [Pubmed]
  15. Mitochondrial import of the ADP/ATP carrier: the essential TIM complex of the intermembrane space is required for precursor release from the TOM complex. Truscott, K.N., Wiedemann, N., Rehling, P., Müller, H., Meisinger, C., Pfanner, N., Guiard, B. Mol. Cell. Biol. (2002) [Pubmed]
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