Tom40 is the main component of the preprotein translocase of the outer membrane of mitochondria (TOM complex). We have isolated Tom40 of Neurospora crassa by removing the receptor Tom22 and the small Tom components Tom6 and Tom7 from the purified TOM core complex. Tom40 is organized in a high molecular mass complex of ∼350 kD. It forms a high conductance channel. Mitochondrial presequence peptides interact specifically with Tom40 reconstituted into planar lipid membranes and decrease the ion flow through the pores in a voltage-dependent manner. The secondary structure of Tom40 comprises ∼31% β-sheet, 22% α-helix, and 47% remaining structure as determined by circular dichroism measurements and Fourier transform infrared spectroscopy. Electron microscopy of purified Tom40 revealed particles primarily with one center of stain accumulation. They presumably represent an open pore with a diameter of ∼2.5 nm, similar to the pores found in the TOM complex. Thus, Tom40 is the core element of the TOM translocase; it forms the protein-conducting channel in an oligomeric assembly.
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11 June 2001
Article|
June 04 2001
Tom40, the Pore-Forming Component of the Protein-Conducting Tom Channel in the Outer Membrane of Mitochondria
Uwe Ahting,
Uwe Ahting
aInstitut für Physiologische Chemie, Universität München, D-81377 München, Germany
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Michel Thieffry,
Michel Thieffry
bLaboratoire de Neurobiologie, Cellulaire et Moléculaire, Centre National de Recherche Scientifique, F-91198 Gif-sur-Yvette, France
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Harald Engelhardt,
Harald Engelhardt
bLaboratoire de Neurobiologie, Cellulaire et Moléculaire, Centre National de Recherche Scientifique, F-91198 Gif-sur-Yvette, France
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Reiner Hegerl,
Reiner Hegerl
cAbteilung für Molekulare Strukturbiologie, Max-Planck Institut für Biochemie, D-82152 Martinsried, Germany
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Walter Neupert,
Walter Neupert
aInstitut für Physiologische Chemie, Universität München, D-81377 München, Germany
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Stephan Nussberger
Stephan Nussberger
aInstitut für Physiologische Chemie, Universität München, D-81377 München, Germany
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Uwe Ahting
aInstitut für Physiologische Chemie, Universität München, D-81377 München, Germany
Michel Thieffry
bLaboratoire de Neurobiologie, Cellulaire et Moléculaire, Centre National de Recherche Scientifique, F-91198 Gif-sur-Yvette, France
Harald Engelhardt
bLaboratoire de Neurobiologie, Cellulaire et Moléculaire, Centre National de Recherche Scientifique, F-91198 Gif-sur-Yvette, France
Reiner Hegerl
cAbteilung für Molekulare Strukturbiologie, Max-Planck Institut für Biochemie, D-82152 Martinsried, Germany
Walter Neupert
aInstitut für Physiologische Chemie, Universität München, D-81377 München, Germany
Stephan Nussberger
aInstitut für Physiologische Chemie, Universität München, D-81377 München, Germany
Abbreviations used in this paper: ATR, attenuated total reflection; CD, circular dichroism; DDM, n-dodecyl β-d-maltoside; FTIR, Fourier transform IR spectroscopy; IR, infrared; Ni-NTA, nickel nitrilotriacetic acid agarose; OG, n-octyl β,d-glucopyranoside; PSC, peptide-sensitive channel; TOM, translocase of the outer mitochondrial membrane; VDAC, voltage-dependent anion channel.
Received:
March 07 2001
Revision Requested:
April 26 2001
Accepted:
April 30 2001
Online ISSN: 1540-8140
Print ISSN: 0021-9525
© 2001 The Rockefeller University Press
2001
The Rockefeller University Press
J Cell Biol (2001) 153 (6): 1151–1160.
Article history
Received:
March 07 2001
Revision Requested:
April 26 2001
Accepted:
April 30 2001
Connected Content
Citation
Uwe Ahting, Michel Thieffry, Harald Engelhardt, Reiner Hegerl, Walter Neupert, Stephan Nussberger; Tom40, the Pore-Forming Component of the Protein-Conducting Tom Channel in the Outer Membrane of Mitochondria. J Cell Biol 11 June 2001; 153 (6): 1151–1160. doi: https://doi.org/10.1083/jcb.153.6.1151
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