Uncoupling of transfer of the presequence and unfolding of the mature domain in precursor translocation across the mitochondrial outer membrane
Uncoupling of transfer of the presequence and unfolding of the mature domain in precursor translocation across the mitochondrial outer membrane
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DOI：
10.1073/pnas.96.7.3634
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发表时间：
1999-03-30
影响因子：
11.1
通讯作者：
Endo, T
中科院分区：
文献类型：
--
作者：
Kanamori, T;Nishikawa, S;Endo, T
线粒体前体蛋白跨线粒体外膜的易位由外膜易位酶（TOM）复合物促进。通过使用位点特异性光交联，我们绘制了TOM蛋白和线粒体前体蛋白之间的相互作用，在两个不同的阶段，阶段A（积累在0摄氏度）和阶段B（积累在30摄氏度），在跨外膜的易位在高分辨率以前没有实现。虽然阶段A和阶段B中间体先前分别被指定为与TOM复合物的顺式位点和反式位点结合的形式，但交联的结果表明，阶段A和阶段B的中间体的前序已经在外膜的反式侧上。成熟结构域在阶段B解折叠并与Tom40结合，而它在阶段A保持折叠。从TOM复合物解离后，阶段B中间体，但不是阶段A中间体，跨内膜的易位由Tom22的膜间空间结构域促进。我们提出了一个新的模型，蛋白质易位跨外膜，易位的前序列和展开的成熟域不一定耦合。
Translocation of mitochondrial precursor proteins across the mitochondrial outer membrane is facilitated by the translocase of the outer membrane (TOM) complex. By using site-specific photocrosslinking, we have mapped interactions between TOM proteins and a mitochondrial precursor protein arrested at two distinct stages, stage A (accumulated at 0 degrees C) and stage B (accumulated at 30 degrees C), in the translocation across the outer membrane at high resolution not achieved previously. Although the stage A and stage B intermediates were assigned previously to the forms bound to the cis site and the trans site of the TOM complex, respectively, the results of crosslinking indicate that the presequence of the intermediates at both stage A and stage B is already on the trans side of the outer membrane. The mature domain is unfolded and bound to Tom40 at stage B whereas it remains folded at stage A. After dissociation from the TOM complex, translocation of the stage B intermediate, but not of the stage A intermediate, across the inner membrane was promoted by the intermembrane-space domain of Tom22. We propose a new model for protein translocation across the outer membrane, where translocation of the presequence and unfolding of the mature domain are not necessarily coupled.