NMR analysis of the closed conformation of syntaxin-1.
NMR analysis of the closed conformation of syntaxin-1.
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DOI：
10.1007/s10858-008-9239-1
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发表时间：
2008-05-01
影响因子：
2.7
通讯作者：
Rizo, Josep
中科院分区：
文献类型：
--
作者：
Chen, Xiaocheng;Lu, Jun;Rizo, Josep
Sec 1/Munc 18（SM）蛋白Munc 18 -1和SNARE突触融合蛋白-1，SNAP-25和突触泡蛋白形成触发神经递质释放的膜融合机制的核心。Munc 18 -1与折叠成闭合构象的突触融合蛋白1结合，并与由三个SNARE形成的SNARE复合物结合，所述SNARE复合物涉及开放的突触融合蛋白1构象。前一种相互作用可能专门用于神经递质释放，而SM蛋白/SNARE复合物相互作用可能是所有类型的细胞内膜融合的关键。目前尚不清楚封闭构象是否在分离的突触融合蛋白-1中高度或仅少量填充，以及Munc 18 -1是否稳定封闭构象或帮助打开它以促进SNARE复合物形成。详细的NMR分析现在表明，封闭的构象几乎定量地填充在分离的syntaxin-1的寡聚化的情况下，并表明其结构是非常相似的，以前观察到的晶体结构的Munc 18 -1/syntaxin-1复合物。此外，我们证明，Munc 18 -1结合防止打开的syntaxin-1封闭构象。这些结果支持了一个模型，其中封闭的构象构成了分离的突触融合蛋白-1的关键内在特性，Munc 18 -1结合稳定了这种构象;在这个模型中，Munc 18 -1在另一个因子帮助打开突触融合蛋白-1构象后的下游事件中起着额外的积极作用。
The Sec1/Munc18 (SM) protein Munc18-1 and the SNAREs syntaxin-1, SNAP-25 and synaptobrevin form the core of the membrane fusion machinery that triggers neurotransmitter release. Munc18-1 binds to syntaxin-1 folded into a closed conformation and to the SNARE complex formed by the three SNAREs, which involves an open syntaxin-1 conformation. The former interaction is likely specialized for neurotransmitter release, whereas SM protein/SNARE complex interactions are likely key for all types of intracellular membrane fusion. It is currently unclear whether the closed conformation is highly or only marginally populated in isolated syntaxin-1, and whether Munc18-1 stabilizes the close conformation or helps to open it to facilitate SNARE complex formation. A detailed NMR analysis now suggests that the closed conformation is almost quantitatively populated in isolated syntaxin-1 in the absence of oligomerization, and indicates that its structure is very similar to that observed previously in the crystal structure of the Munc18-1/syntaxin-1 complex. Moreover, we demonstrate that Munc18-1 binding prevents opening of the syntaxin-1 closed conformation. These results support a model whereby the closed conformation constitutes a key intrinsic property of isolated syntaxin-1 and Munc18-1 binding stabilizes this conformation; in this model, Munc18-1 plays in addition an active role in downstream events after another factor(s) helps to open the syntaxin-1 conformation.