Tom22 is a multifunctional organizer of the mitochondrial preprotein translocase. |
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Authors: | S van Wilpe M T Ryan K Hill A C Maarse C Meisinger J Brix P J Dekker M Moczko R Wagner M Meijer B Guiard A H?nlinger N Pfanner |
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Affiliation: | Institute for Molecular Cell Biology, BioCentrum Amsterdam, The Netherlands. |
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Abstract: | Mitochondrial preproteins are imported by a multisubunit translocase of the outer membrane (TOM), including receptor proteins and a general import pore. The central receptor Tom22 binds preproteins through both its cytosolic domain and its intermembrane space domain and is stably associated with the channel protein Tom40 (refs 11-13). Here we report the unexpected observation that a yeast strain can survive without Tom22, although it is strongly reduced in growth and the import of mitochondrial proteins. Tom22 is a multifunctional protein that is required for the higher-level organization of the TOM machinery. In the absence of Tom22, the translocase dissociates into core complexes, representing the basic import units, but lacks a tight control of channel gating. 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. Thus a preprotein translocase can combine receptor functions with distinct organizing roles in a multidomain protein. |
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