The β subunit of the Sec61 complex facilitates cotranslational protein transport and interacts with the signal peptidase during translocation
The β subunit of the Sec61 complex facilitates cotranslational protein transport and interacts with the signal peptidase during translocation
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DOI：
10.1083/jcb.141.4.887
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发表时间：
1998-05-18
影响因子：
7.8
通讯作者：
Hartmann, E
中科院分区：
文献类型：
--
作者：
Kalies, KU;Rapoport, TA;Hartmann, E
Sec 61复合物是内质网膜蛋白质转运装置的中心组成部分。我们已经解决了β亚基（Sec 61 β）在共翻译蛋白易位过程中的作用。与重建系统，我们表明，Sec 61复合物缺乏Sec 61 β基本上是无活性的，当伸长和膜靶向新生链同时发生。易位过程在新生链将插入易位通道的步骤处被扰动。然而，如果给予新生多肽与突变体Sec 61复合物的相互作用足够的时间，易位几乎是正常的。因此，Sec 61 β动力学促进共翻译translation，但不是必不可少的it. Using化学交联，我们表明，Sec 61 β不仅与亚基的Sec 61复合物，但也与25-kD亚基的信号肽酶复合物（SPC 25），从而首次证明SPC和Sec 61复合物之间的紧密相互作用。有趣的是，Sec 61 β和SPC 25之间以及Sec 61 β和Sec 61 α之间的交联依赖于膜结合核糖体的存在，这表明这些相互作用在易位开始时被诱导。我们认为SPC被瞬时募集到易位位点，从而增强其活性。
The Sec61 complex is the central component of the protein translocation apparatus of the ER membrane. We have addressed the role of the beta subunit (Sec61 beta) during cotranslational protein translocation. With a reconstituted system, we show that a Sec61 complex lacking Sec61 beta is essentially inactive when elongation and membrane targeting of a nascent chain occur at the same time. The translocation process is perturbed at a step where the nascent chain would be inserted into the translocation channel. However, if sufficient time is given for the interaction of the nascent polypeptide with the mutant Sec61 complex, translocation is almost normal. Thus Sec61 beta kinetically facilitates cotranslational translocation, but is not essential for it. Using chemical cross-linking we show that Sec61 beta not only interacts with subunits of the Sec61 complex but also with the 25-kD subunit of the signal peptidase complex (SPC25), thus demonstrating for the first time a tight interaction between the SPC and the Sec61 complex. Interestingly, the cross-links between Sec61 beta and SPC25 and between Sec61 beta and Sec61 alpha depend on the presence of membrane-bound ribosomes, suggesting that these interactions are induced when translocation is initiated. We propose that the SPC is transiently recruited to the translocation site, thus enhancing its activity.