Interaction of mitochondrial targeting signals with acidic receptor domains along the protein import pathway: evidence for the 'acid chain' hypothesis
Interaction of mitochondrial targeting signals with acidic receptor domains along the protein import pathway: evidence for the 'acid chain' hypothesis
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DOI：
10.1093/emboj/17.14.3886
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发表时间：
1998-07-15
期刊：
影响因子：
11.4
通讯作者：
Mihara, K
中科院分区：
文献类型：
--
作者：
Komiya, T;Rospert, S;Mihara, K
具有碱性靶向信号的线粒体前体蛋白可以通过顺序结合到亲和力增加的酸性受体位点而跨外膜转运。为了验证这一“酸链”假说，我们测定了线粒体前体与三个酸性受体结构域的相互作用：Tom20的胞质结构域和Tom22和Tim23的膜间空间结构域。前体结合的表观亲和力和耐盐性以Tom20 < Tom22（内部）< Tim23的顺序增加。过量的靶向肽抑制了前体与三个酸性受体结构域和Tom70的纯胞质结构域的结合，但不抑制同样碱性的对照肽。在这种无膜和限定的系统中，与Tom70或Tom20结构域预结合的前体被有效地转移到Tim23结构域。内部Tom22结构域刺激转移，并且在相反方向上效率低得多。预定用于外膜的前体仅结合Tom20，但不结合内部Tom22或Tim23结构域，并且预定用于内膜的前体仅结合Tom20和内部Tom22结构域，但不结合Tim23结构域。这些结果表明，特异性和顺序结合的靶向信号的战略定位的酸性受体提供了一个前体跨外膜，并有助于进口蛋白质的线粒体内分选。
Mitochondrial precursor proteins with basic targeting signals may be transported across the outer membrane by sequential binding to acidic receptor sites of increasing affinity. To test this 'acid chain' hypothesis, we assayed the interaction of mitochondrial precursors with three acidic receptor domains: the cytosolic domain of Tom20 and the intermembrane space domain of Tom22 and Tim23, The apparent affinity and salt resistance of precursor binding increased in the order Tom20 < Tom22 (internal) < Tim23. Precursor binding to the three acidic receptor domains and to the pure cytosolic domain of Tom70 was inhibited by excess targeting peptide, but not by an equally basic control peptide, In this membrane-free and defined system, a precursor pre-bound to the Tom70 or Tom20 domain was transferred efficiently to the Tim23 domain. Transfer was stimulated by the internal Tom22 domain and was much less efficient in the reverse direction. Precursors destined for the outer membrane bound only to Tom20, but not to the internal Tom22 or the Tim23 domain, and a precursor destined for the inner membrane bound only to the Tom20 and the internal Tom22 domain, but not to the Tim23 domain. These results suggest that specific and sequential binding of a targeting signal to strategically situated acidic receptors delivers a precursor across the outer membrane and contributes to intramitochondrial sorting of imported proteins.