Dynamics of the TOM complex of mitochondria during binding and translocation of preproteins.
Translocation of preproteins across the mitochondrial outer membrane is mediated by the TOM complex. This complex consists of receptor components for the initial contact with preproteins at the mitochondrial surface and membrane-embedded proteins which promote transport and form the translocation pore. In order to understand the interplay between the translocating preprotein and the constituents of the TOM complex, we analyzed the dynamics of the TOM complex of Neurospora crassa and Saccharomyces cerevisiae mitochondria by following the structural alterations of the essential pore component Tom40 during the translocation of preproteins. Tom40 exists in a homo-oligomeric assembly and dynamically interacts with Tom6. The Tom40 assembly is influenced by a block of negatively charged amino acid residues in the cytosolic domain of Tom22, indicating a cross-talk between preprotein receptors and the translocation pore. Preprotein binding to specific sites on either side of the outer membrane (cis and trans sites) induces distinct structural alterations of Tom40. To a large extent, these changes are mediated by interaction with the mitochondrial targeting sequence. We propose that such targeting sequence-induced adaptations are a critical feature of translocases in order to facilitate the movement of preproteins across cellular membranes.
Institut für Physiologische Chemie, Physikalische Biochemie und Zellbiologie der Universität München, 80336 Munich, Germany.
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D000906:Antibodies; D002850:Chromatography, Gel; D003432:Cross-Linking Reagents / Q000494:pharmacology; D005656:Fungal Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008727:Methotrexate / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D008970:Molecular Weight; D009492:Neurospora crassa / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011956:Receptors, Cell Surface; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D014508:Urea
D000906:Antibodies; D003432:Cross-Linking Reagents; D005656:Fungal Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D011498:Protein Precursors; D011956:Receptors, Cell Surface; D029701:Saccharomyces cerevisiae Proteins; C090857:TOM22 protein, S cerevisiae; C066555:Tom40 protein, S cerevisiae; D014508:Urea; D008727:Methotrexate