Calcium sensitive ring-like oligomers formed by synaptotagmin.
Calcium sensitive ring-like oligomers formed by synaptotagmin.
复制标题
由突触结合蛋白形成的钙敏感环状寡聚物。
DOI：
10.1073/pnas.1415849111
复制
发表时间：
2014
影响因子：
11.1
通讯作者：
Rothman,JamesE
中科院分区：
文献类型：
--
作者：
Wang,Jing;Bello,Oscar;Auclair,SarahM;Wang,Jing;Coleman,Jeff;Pincet,Frederic;Krishnakumar,ShyamS;Sindelar,CharlesV;Rothman,JamesE
突触囊泡蛋白synaptotagmin-1（SYT）是偶联钙离子流入膜融合机器所必需的。然而，这一过程背后的结构机制尚不清楚。在这里，我们报告了一个意想不到的圆形排列（环）SYT的胞质结构域（C2 AB）形成的脂质单层在没有游离钙离子的情况下，通过电子显微镜显示。环的直径从18-43 nm不等，对应于11-26个SYT分子。SYT环的连续堆叠偶尔会将脂质单层和双层转化为蛋白质包被的管。SYT管的螺旋重建显示，其中一个C2结构域（基于其生化性质，最有可能是C2B）与膜相互作用并参与环的形成，另一个C2结构域径向向外指向。SYT环被生理浓度的游离钙迅速破坏，但不被镁破坏。假设不含钙的SYT环是生理相关的，这些结果表明SYT调节神经递质释放的一种简单而新颖的机制：该环作为间隔物阻止可溶性N-乙基马来酰亚胺敏感因子激活蛋白受体（SNARE）复合物组装的完成，从而在缺乏钙的情况下夹紧融合。当环在钙的存在下分解时，融合不受阻碍地进行。
The synaptic vesicle protein synaptotagmin-1 (SYT) is required to couple calcium influx to the membrane fusion machinery. However, the structural mechanism underlying this process is unclear. Here we report an unexpected circular arrangement (ring) of SYT’s cytosolic domain (C2AB) formed on lipid monolayers in the absence of free calcium ions as revealed by electron microscopy. Rings vary in diameter from 18–43 nm, corresponding to 11–26 molecules of SYT. Continuous stacking of the SYT rings occasionally converts both lipid monolayers and bilayers into protein-coated tubes. Helical reconstruction of the SYT tubes shows that one of the C2 domains (most likely C2B, based on its biochemical properties) interacts with the membrane and is involved in ring formation, and the other C2 domain points radially outward. SYT rings are disrupted rapidly by physiological concentrations of free calcium but not by magnesium. Assuming that calcium-free SYT rings are physiologically relevant, these results suggest a simple and novel mechanism by which SYT regulates neurotransmitter release: The ring acts as a spacer to prevent the completion of the solubleN-ethylmaleimide–sensitive factor activating protein receptor (SNARE) complex assembly, thereby clamping fusion in the absence of calcium. When the ring disassembles in the presence of calcium, fusion proceeds unimpeded.