A conformational switch in syntaxin during exocytosis:: role of munc18
A conformational switch in syntaxin during exocytosis:: role of munc18
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DOI：
10.1093/emboj/18.16.4372
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发表时间：
1999-08-16
期刊：
影响因子：
11.4
通讯作者：
Rizo, J
中科院分区：
文献类型：
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作者：
Dulubova, I;Sugita, S;Rizo, J
Syntaxin 1是突触膜融合的重要蛋白质，它包含一个螺旋状的自主折叠的N端结构域、一个C端SNARE区和一个跨膜区。SNARE蛾绑定到synaptobrevin和SNAP-25组装的核心复合物，而几乎整个细胞质序列参与与munc 18 -1，神经元Sec 1同系物的复合物，我们现在证明，通过NMR光谱，在隔离，syntaxin采用了“封闭”的构象。突触融合蛋白的这种默认构象与需要开放突触融合蛋白构象的核心复合物组装不相容。使用定点突变，我们发现封闭构象的破坏会消除突触融合蛋白与munc 18 -1结合并抑制PC 12细胞分泌的能力。这些结果表明，syntaxin结合到munc 18 -1在一个封闭的构象，并建议，这种构象代表一个必不可少的中间体在胞吐，我们的数据表明一个模型，其中，在胞吐，syntaxin经历了一个大的构象开关，介导的syntaxin-munc 18 -1复合物和核心复合物之间的过渡。
Syntaxin 1, an essential protein in synaptic membrane fusion, contains a helical autonomously folded N-terminal domain, a C-terminal SNARE moth and a transmembrane region. The SNARE moth binds to synaptobrevin and SNAP-25 to assemble the core complex, whereas almost the entire cytoplasmic sequence participates in a complex with munc18-1, a neuronal Sec1 homolog, We now demonstrate by NMR spectroscopy that, in isolation, syntaxin adopts a 'closed' conformation. This default conformation of syntaxin is incompatible with core complex assembly which requires an open' syntaxin conformation. Using site-directed mutagenesis, we find that disruption of the closed conformation abolishes the ability of syntaxin to bind to munc18-1 and to inhibit secretion in PC12 cells. These results indicate that syntaxin binds to munc18-1 in a closed conformation and suggest that this conformation represents an essential intermediate in exocytosis, Our data suggest a model whereby, during exocytosis, syntaxin undergoes a large conformational switch that mediates the transition between the syntaxin-munc18-1 complex and the core complex.