Two conformations of the Tom20 preprotein receptor in the TOM holo complex.

Pamela Ornelas, Thomas Bausewein, Janosch Martin, Nina Morgner, Stephan Nussberger, Werner Kühlbrandt

Proceedings of the National Academy of Sciences of the United States of America 2023 Aug 22

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The TOM complex is the main entry point for precursor proteins (preproteins) into mitochondria. Preproteins containing targeting sequences are recognized by the TOM complex and imported into mitochondria. We have determined the structure of the TOM core complex from Neurospora crassa by single-particle electron cryomicroscopy at 3.3 Å resolution, showing its interaction with a bound preprotein at 4 Å resolution, and of the TOM holo complex including the Tom20 receptor at 6 to 7 Å resolution. TOM is a transmembrane complex consisting of two β-barrels, three receptor subunits, and three short transmembrane subunits. Tom20 has a transmembrane helix and a receptor domain on the cytoplasmic side. We propose that Tom20 acts as a dynamic gatekeeper, guiding preproteins into the pores of the TOM complex. We analyze the interactions of Tom20 with other TOM subunits, present insights into the structure of the TOM holo complex, and suggest a translocation mechanism.

Citation

Pamela Ornelas, Thomas Bausewein, Janosch Martin, Nina Morgner, Stephan Nussberger, Werner Kühlbrandt. Two conformations of the Tom20 preprotein receptor in the TOM holo complex. Proceedings of the National Academy of Sciences of the United States of America. 2023 Aug 22;120(34):e2301447120