The Tim9p/10p and Tim8p/13p complexes bind to specific sites on Tim23p during mitochondrial protein import
The Tim9p/10p and Tim8p/13p complexes bind to specific sites on Tim23p during mitochondrial protein import
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DOI：
10.1091/mbc.e06-06-0546
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发表时间：
2007-02-01
影响因子：
3.3
通讯作者：
Johnson, Arthur E.
中科院分区：
文献类型：
--
作者：
Davis, Alison J.;Alder, Nathan N.;Johnson, Arthur E.
膜间隙（IMS）中的Tim9p/Tim10p和Tim8p/Tim13p蛋白复合物促进了多聚膜蛋白进入线粒体内膜（IM）。这些复合物被提出作为伴侣，通过水相IMS运输疏水性IM蛋白并阻止其聚集。为了研究这种相互作用的性质，在没有IM电位的情况下，将含有单个光反应性交联探针的Tim23p分子导入线粒体，在那里它们与IMS中的小Tim复合物相关。在光解和免疫沉淀中，位于特定Tim23p位点的探针（检查了27个不同的位置）被发现在大多数情况下仅与一个小的Tim蛋白发生共价反应。因此，Tim8p、Tim9p、Tim10p和Tim13p在整合到IM之前被定位在Tim23p底物的特定位点附近。这种与Tim23p结合的特异性强烈表明，小的Tim蛋白不仅可以通过最小化非极性Tim23p表面暴露于水介质中而仅作为一般伴侣，而且还可以将折叠的Tim23p底物排列在适当的方向上，以便在TIM22转座子上传递和整合到IM中。
The import of polytopic membrane proteins into the mitochondrial inner membrane (IM) is facilitated by Tim9p/Tim10p and Tim8p/Tim13p protein complexes in the intermembrane space (IMS). These complexes are proposed to act, as chaperones by transporting the hydrophobic IM proteins through the aqueous IMS and preventing their aggregation. To examine the nature of this interaction, Tim23p molecules containing a single photoreactive cross-linking probe were imported into mitochondria in the absence of an IM potential where they associated with small Tim complexes in the IMS. On photolysis and immunoprecipitation, a probe located at a particular Tim23p site (27 different locations were examined) was found to react covalently with, in most cases, only one of the small Tim proteins. Tim8p, Tim9p, Tim10p, and Tim13p were therefore positioned adjacent to specific sites in the Tim23p substrate before its integration into the IM. This specificity of binding to Tim23p strongly suggests that small Tim proteins do not function solely as general chaperones by minimizing the exposure of nonpolar Tim23p surfaces to the aqueous medium, but may also align a folded Tim23p substrate in the proper orientation for delivery and integration into the IM at the TIM22 translocon.