Unwin N
MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
J Struct Biol. 1998;121(2):181-90. doi: 10.1006/jsbi.1997.3949.
The nicotinic acetylcholine receptor is a neurotransmitter-gated ion channel that mediates the rapid propagation of electrical signals at the nerve-muscle synapse. Its structure at 9 A resolution, in both the closed- and the open-channel forms, has been examined by electron microscopy of tubular crystals grown from Torpedo postsynaptic membranes. Binding of acetylcholine to open the channel causes a localized disturbance in the extracellular domain and initiates small rotations of the protein subunits, which trigger a change in configuration of alpha-helices lining the membrane-spanning pore. A method recently developed to correct in three dimensions for distortions present in the crystals, combined with improvements in the electron imaging, should eventually allow these conformational changes to be seen at atomic resolution.
烟碱型乙酰胆碱受体是一种神经递质门控离子通道，介导神经肌肉突触处电信号的快速传播。通过对从电鳐突触后膜生长的管状晶体进行电子显微镜检查，已研究了其9埃分辨率下的结构，包括关闭通道和开放通道形式。乙酰胆碱结合打开通道会在细胞外结构域引起局部扰动，并引发蛋白质亚基的小旋转，进而触发跨膜孔道内衬α螺旋的构象变化。最近开发的一种在三维空间校正晶体中存在的畸变的方法，与电子成像技术的改进相结合，最终应能使这些构象变化在原子分辨率下得以观察。
