In vitro studies with purified components reveal signal recognition particle (SRP) and SecA SecB as constituents of two independent protein-targeting pathways of Escherichia coli
In vitro studies with purified components reveal signal recognition particle (SRP) and SecA SecB as constituents of two independent protein-targeting pathways of Escherichia coli
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DOI：
10.1091/mbc.10.7.2163
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发表时间：
1999-07-01
影响因子：
3.3
通讯作者：
Müller, M
中科院分区：
文献类型：
--
作者：
Koch, HG;Hengelage, T;Müller, M
比较了分泌蛋白跨膜转运和膜蛋白整合到大肠杆菌质膜的分子要求。这是在一种新的无细胞系统中实现的。大肠杆菌，通过广泛的亚分级，同时使SecA/SecB和信号识别颗粒（SRP）组件，Ffh（P48），4.5S RNA，和FtsY缺陷。两种膜蛋白整合到E. coli需要所有三种SRP组分，并且不能由SecA、SecB和Δ mu H+驱动。与此相反，这些是唯一的组件所需的易位分泌蛋白进入膜囊泡，在这个过程中，SRP组件是完全无活性的。我们的结果，同时证实了以前的体内研究，提供了第一个在体外证据的依赖性，多位内膜蛋白的整合对SRP在E。杆菌此外，它们表明SRP和SecA/SecB具有不同的底物特异性，导致E.杆菌两种靶向途径在易位孔处相交，因为它们同样受到阻断的易位通道的影响。
The molecular requirements for the translocation of secretory proteins across, and the integration of membrane proteins into, the plasma membrane of Escherichia coli were compared. This was achieved in a novel cell-free system from E. coli which, by extensive subfractionation, was simultaneously rendered deficient in SecA/SecB and the signal recognition particle (SRP) components, Ffh (P48), 4.5S RNA, and FtsY. The integration of two membrane proteins into inside-out plasma membrane vesicles of E. coli required all three SRP components and could not be driven by SecA, SecB, and Delta mu H+. In contrast, these were the only components required for the translocation of secretory proteins into membrane vesicles, a process in which the SRP components were completely inactive. Our results, while confirming previous in vivo studies, provide the first in vitro evidence for the dependence of the integration of polytopic inner membrane proteins on SRP in E. coli. Furthermore, they suggest that SRP and SecA/SecB have different substrate specificities resulting in two separate targeting mechanisms for membrane and secretory proteins in E. coli. Both targeting pathways intersect at the translocation pore because they are equally affected by a blocked translocation channel.