Visualization of a polytopic membrane protein during SecY-mediated membrane insertion
Visualization of a polytopic membrane protein during SecY-mediated membrane insertion
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DOI：
10.1038/ncomms5103
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发表时间：
2014-06-01
影响因子：
16.6
通讯作者：
Beckmann, Roland
中科院分区：
文献类型：
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作者：
Bischoff, Lukas;Wickles, Stephan;Beckmann, Roland
多位膜蛋白的生物发生发生在核糖体上，核糖体与膜嵌入的蛋白质传导通道紧密结合：sec复合物。核糖体和sec复合体内新生蛋白质所遵循的路径相对较好地确定；然而，目前尚不清楚多聚膜蛋白的n端跨膜结构域（TMDs）在c端跨膜结构域尚未合成时的命运。在这里，我们展示了体内生成的核糖体- secy复合体的亚纳米低温电镜结构，该复合体携带一种膜插入介质变形紫质（PR）。该结构揭示了一个预打开的sec复合物和已经在sec复合物外的PR的前两个tmd直接在其拟议的侧门前。因此，我们的结构与n端TMDs在SecY外围的定位一致，并且为膜蛋白拓扑形成的分子机制提供了线索。
The biogenesis of polytopic membrane proteins occurs co-translationally on ribosomes that are tightly bound to a membrane-embedded protein-conducting channel: the Sec-complex. The path that is followed by nascent proteins inside the ribosome and the Sec-complex is relatively well established; however, it is not clear what the fate of the N-terminal transmembrane domains (TMDs) of polytopic membrane proteins is when the C-terminal TMDs domains are not yet synthesized. Here, we present the sub-nanometer cryo-electron microscopy structure of an in vivo generated ribosome-SecY complex that carries a membrane insertion intermediate of proteorhodopsin (PR). The structure reveals a pre-opened Sec-complex and the first two TMDs of PR already outside the SecY complex directly in front of its proposed lateral gate. Thus, our structure is in agreement with positioning of N-terminal TMDs at the periphery of SecY, and in addition, it provides clues for the molecular mechanism underlying membrane protein topogenesis.