Subunit structure of a mammalian ER/Golgi SNARE complex
Subunit structure of a mammalian ER/Golgi SNARE complex
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DOI：
10.1074/jbc.m007684200
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发表时间：
2000-12-15
影响因子：
4.8
通讯作者：
Hay, JC
中科院分区：
文献类型：
--
作者：
Xu, DL;Joglekar, AP;Hay, JC
SNAP受体（SNARE）复合物桥接相对的膜以促进分泌和内体途径内的膜融合。因为只有胞吐SNARE复合物已被详细表征，所以来自不同融合步骤的SNARE复合物所共有的结构特征尚不清楚。我们现在描述的亚基结构，装配和调节的四级陷阱复合物，这似乎介导的早期步骤，内质网（ER）高尔基体运输。纯化的重组syntaxin 5、membrane和rbet 1，三个Q-SNARE，协同组装以产生针对R-SNARE sec 22 b的高亲和力结合位点。突触融合蛋白5氨基末端结构域有效抑制SNARE复合物组装。ER/高尔基体四元复合物是非常相似的突触复合物，这表明一个共同的模式是遵循在所有的运输步骤，其中三个Q-螺旋组装形成一个高亲和力的结合位点的第四个R-螺旋上的相对膜。有趣的是，虽然sec 22 b结合到syntaxin 5，membrane和rbet 1的组合，它只能结合，如果它存在，而其他组装; sec 22 b不能结合到预先组装的三元复合物syntaxin 5，membrane和rbet 1。最后，我们证明了含有sec 22 b的四元复合物不仅是体外实体，而且是活细胞中的真正物种。
SNAP receptor (SNARE) complexes bridge opposing membranes to promote membrane fusion within the secretory and endosomal pathways. Because only the exocytic SNARE complexes have been characterized in detail, the structural features shared by SNARE complexes from different fusion steps are not known. We now describe the subunit structure, assembly, and regulation of a quaternary SNARE complex, which appears to mediate an early step in endoplasmic reticulum (ER) to Golgi transport. Purified recombinant syntaxin 5, membrin, and rbet1, three Q-SNAREs, assemble cooperatively to create a high affinity binding site for sec22b, an R-SNARE. The syntaxin 5 amino-terminal domain potently inhibits SNARE complex assembly. The ER/Golgi quaternary complex is remarkably similar to the synaptic complex, suggesting that a common pattern is followed at all transport steps, where three Q-helices assemble to form a high affinity binding site for a fourth R-helix on an opposing membrane. Interestingly, although sec22b binds to the combination of syntaxin 5, membrin, and rbet1, it can only bind if it is present while the others assemble; sec22b cannot bind to a pre-assembled ternary complex of syntaxin 5, membrin, and rbet1. Finally, we demonstrate that the quaternary complex containing sec22b is not an in vitro entity only, but is a bona fide species in living cells.