Brix J, Ziegler G A, Dietmeier K, Schneider-Mergener J, Schulz G E, Pfanner N
Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, Freiburg, D-79104, Germany.
J Mol Biol. 2000 Nov 3;303(4):479-88. doi: 10.1006/jmbi.2000.4120.
The mitochondrial import receptor of 70 kDa, Tom70, preferentially recognizes precursors of membrane proteins with internal targeting signals. We report the identification of a stably folded 25 kDa core domain located in the middle portion of Tom70 that contains two of the seven tetratricopeptide repeat motifs of the receptor. The core domain binds non-cleavable and cleavable preproteins carrying internal targeting signals with a specificity indistinguishable from the full-length receptor. Competition studies indicate that both types of preproteins interact with overlapping binding sites of the core domain and that at least one additional interaction site is present in the full-length receptor. We suggest a model of Tom70 function in import of membrane proteins whereby a hydrophobic preprotein concomitantly interacts with several binding sites of the receptor.
70 kDa的线粒体输入受体Tom70优先识别带有内部靶向信号的膜蛋白前体。我们报告了在Tom70中间部分鉴定出一个稳定折叠的25 kDa核心结构域，该结构域包含受体七个四肽重复基序中的两个。该核心结构域结合携带内部靶向信号的不可切割和可切割前体蛋白，其特异性与全长受体无异。竞争研究表明，这两种类型的前体蛋白与核心结构域的重叠结合位点相互作用，并且全长受体中至少存在一个额外的相互作用位点。我们提出了一个Tom70在膜蛋白输入中的功能模型，即疏水性前体蛋白与受体的多个结合位点同时相互作用。
