Visualization of Distinct Entities of the SecYEG Translocon during Translocation and Integration of Bacterial Proteins
Visualization of Distinct Entities of the SecYEG Translocon during Translocation and Integration of Bacterial Proteins
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DOI：
10.1091/mbc.e08-08-0886
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发表时间：
2009-03-15
影响因子：
3.3
通讯作者：
Koch, Hans-Georg
中科院分区：
文献类型：
--
作者：
Boy, Diana;Koch, Hans-Georg
普遍保守的SecYEG/Sec61易位是细菌胞质膜和真核生物内质网膜的主要蛋白质传导通道。它既参与分泌蛋白的跨膜转运，也参与将膜蛋白整合到膜的脂质期。在目前的研究中，我们已经在天然大肠杆菌膜中检测到不同的SecYEG易位复合物。Blue-Native-PAGE显示静息膜中存在200 kda的SecYEG复合物。当seca依赖性分泌蛋白pOmpA被捕获在SecYEG通道中时，观察到一个较小的类似于140-kDa的含secy复合物，这可能对应于一个单体SecYEG-底物复合物。在SecYEG转座子中捕获srp依赖的多聚膜蛋白甘露醇渗透酶，产生两个250和600 kDa的复合物，每个复合物都含有SecY和转座子相关的膜蛋白YidC。这两种复合物的出现与甘露醇渗透酶靶向膜时暴露的跨膜结构域的数量有关。这些结果表明，细菌SecYEG转座子的组装或稳定性受到需要运输的底物的影响。
The universally conserved SecYEG/Sec61 translocon constitutes the major protein-conducting channel in the cytoplasmic membrane of bacteria and the endoplasmic reticulum membrane of eukaryotes. It is engaged in both translocating secretory proteins across the membrane as well as in integrating membrane proteins into the lipid phase of the membrane. In the current study we have detected distinct SecYEG translocon complexes in native Escherichia coli membranes. Blue-Native-PAGE revealed the presence of a 200-kDa SecYEG complex in resting membranes. When the SecA-dependent secretory protein pOmpA was trapped inside the SecYEG channel, a smaller SecY-containing complex of similar to 140-kDa was observed, which probably corresponds to a monomeric SecYEG-substrate complex. Trapping the SRP-dependent polytopic membrane protein mannitol permease in the SecYEG translocon, resulted in two complexes of 250 and 600 kDa, each containing both SecY and the translocon-associated membrane protein YidC. The appearance of both complexes was correlated with the number of transmembrane domains that were exposed during targeting of mannitol permease to the membrane. These results suggest that the assembly or the stability of the bacterial SecYEG translocon is influenced by the substrate that needs to be transported.