The Croonian Lecture 2000. Nicotinic acetylcholine receptor and the structural basis of fast synaptic transmission

Communication in the nervous system takes place at chemical and electrical synapses, where neurotransmitter-gated ion channels, such as the nicotinic acetylcholine (ACh) receptor, and gap junction channels control propagation of electrical signals from one cell to the next. Newly developed electron crystallographic methods have revealed the structures of these channels tra pped in open as well as closed states, suggesting how they work. The ACh re ceptor has large vestibules extending from the membrane which shape the ACh -binding pockets and facilitate selective transport of cations across a nar row membrane-spanning pore. When ACh enters the pockets it triggers a conce rted conformational change that opens the pore by destabilizing a gate in t he middle of the membrane made by a ring of pore-lining a-helical segments. The alternative 'open' configuration of pore-lining segments reshapes the lumen and creates new surfaces, allowing the ions to pass through. The gap junction channel uses a similar structural mechanism, involving coordinated rearrangements of alpha -helical segments in the plane of the membrane, to open its pore.