The three modules of ADP/ATP carrier cooperate in receptor recruitment and translocation into mitochondria.
The ADP/ATP carrier (AAC) is a major representative of mitochondrial preproteins lacking an N-terminal presequence. AAC contains targeting information in each of its three modules, which has led to a search for the dominant targeting region. An alternative, not yet tested model would be that several distinct targeting signals function simultaneously in import of the preprotein. We report that the three AAC modules cooperate in binding to the receptor Tom70 such that three Tom70 dimers are recruited to one preprotein. The modules are transferred to the import pore in a stepwise manner and cooperate again in the accumulation of AAC in the general import pore complex. AAC can cross the outer membrane with an internal segment first, i.e. in a loop formation. Each module of AAC is required for dimerization in the inner membrane. We propose a new concept for import of the hydrophobic carrier proteins into mitochondria where multiple signals cooperate in receptor recruitment, outer membrane translocation via loop formation and assembly in the inner membrane.
Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany.
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Wiedemann
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Pfanner
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Ryan
D000255:Adenosine Triphosphate / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000378:metabolism; D019281:Dimerization; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008727:Methotrexate / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D011485:Protein Binding; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013388:Succinimides / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics / Q000378:metabolism
D003432:Cross-Linking Reagents; D005656:Fungal Proteins; D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D013388:Succinimides; C489039:TOM70 protein, S cerevisiae; C072252:m-maleimidobenzoyl-N-hydroxysulfosuccinimide ester; D000255:Adenosine Triphosphate; D000226:Mitochondrial ADP, ATP Translocases; D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate