Structure and action of the nicotinic acetylcholine receptor explored by electron microscopy

The nicotinic acetylcholine (ACh) receptor is the transmitter-gated ion channel at the nerve/muscle synapse. Electron microscopical experiments on isolated postsynaptic membranes have determined the structure of this channel and how the structure changes upon activation. When ACh enters the ligand-binding domain it initiates rotations of the protein chains on opposite sides of the entrance to the membrane-spanning pore. These rotations are communicated to the pore-lining a-helices and open the gate - a constricting hydrophobic girdle at the middle of the membrane - by breaking it apart. The movements are small and involve energetically favourable displacements parallel to the membrane plane. (C) 2003 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.