Different transmembrane domains associate with distinct endoplasmic reticulum components during membrane integration of a polytopic protein
Different transmembrane domains associate with distinct endoplasmic reticulum components during membrane integration of a polytopic protein
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DOI：
10.1091/mbc.e02-04-0198
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发表时间：
2002-12-01
影响因子：
3.3
通讯作者：
High, S
中科院分区：
文献类型：
--
作者：
Meacock, SL;Lecomte, FJL;High, S
我们一直在研究七个跨膜结构域（TM）蛋白质视蛋白的插入，以深入了解多位蛋白质的多个TM是如何整合在内质网（ER）。我们发现与新生视蛋白多肽链的第一和第二TM相关的ER组分是明显不同的。第一个TM（TM 1）与Sec 61复合物的α和β亚基相邻，是一种新的组分，一种与10 kDa ER易位子（PAT-10）相关的蛋白质。PAT-10最显著的特征是，在全长视蛋白多肽的生物发生和膜整合过程中，它始终与TM 1相邻。TM 2在其膜整合过程中也被发现与Sec 61 α和Sec 61 β相邻。然而，TM 2不与PAT-10形成任何加合物;相反，观察到与TRAM蛋白的瞬时缔合。我们发现，PAT-10与视蛋白TM 1的关联不需要新生链的N-糖基化，并且与TM 1的氨基酸序列和跨膜拓扑结构无关。我们的结论是，ER膜插入位点的精确组成可以是不同的跨膜结构域的多位蛋白。我们发现，一个特定的TM的环境可以影响新生链生物合成达到的“阶段”，和TM的相对位置内的多肽。
We have been studying the insertion of the seven transmembrane domain (TM) protein opsin to gain insights into how the multiple TMs of polytopic proteins are integrated at the endoplasmic reticulum (ER). We find that the ER components associated with the first and second TMs of the nascent opsin polypeptide chain are clearly distinct. The first TM (TM1) is adjacent to the alpha and beta subunits of the Sec61 complex, and a novel component, a protein associated with the ER translocon of 10 kDa (PAT-10). The most striking characteristic of PAT-10 is that it remains adjacent to TM1 throughout the biogenesis and membrane integration of the full-length opsin polypeptide. TM2 is also found to be adjacent to Sec61alpha and Sec61beta during its membrane integration. However; TM2 does not form any adducts with PAT-10; rather, a transient association with the TRAM protein is observed. We show that the association of PAT-10 with opsin TM1 does not require the N-glycosylation of the nascent chain and occurs irrespective of the amino acid sequence and transmembrane topology of TM1. We conclude that the precise makeup of the ER membrane insertion site can be distinct for the different transmembrane domains of a polytopic protein. We find that the environment of a particular TM can be influenced by both the "stage" of nascent chain biosynthesis reached, and the TM's relative location within the polypeptide.