Differential Recognition of Preproteins by the Purified Cytosolic Domains of the Mitochondrial Import Receptors Tom20, Tom22, and Tom70

作者：Jan Brix, Klaus Dietmeier, Nikolaus Pfanner · 发表于：Journal of Biological Chemistry · 年份：1997 · DOI：10.1074/jbc.272.33.20730 · 被引用次数：294 · 研究领域：Mitochondrial Function and Pathology、RNA modifications and cancer、RNA and protein synthesis mechanisms

The preprotein translocase of the outer mitochondrial membrane (Tom) is a multi-subunit complex required for specific recognition and membrane translocation of nuclear-encoded preproteins. We have expressed and purified the cytosolic domains of three postulated import receptors, Tom20, Tom22, and Tom70. Each receptor domain is able to bind mitochondrial preproteins but with different specificity. Tom20 binds both preproteins with N-terminal presequences and preproteins with internal targeting signals; the binding is enhanced by the addition of salt. Tom22 selectively recognizes presequence-carrying preproteins in a salt-sensitive manner. Tom70 preferentially binds preproteins with internal targeting information. A chemically synthesized presequence peptide competes with preproteins for binding to Tom20 and Tom22 but not to Tom70. We conclude that each of the three import receptors binds preproteins independently and by a different mechanism. Both Tom20 and Tom22 function as presequence receptors.