Ligand-gated pentameric ion channels, from binding to gating.

X-ray structures of molluscan acetylcholine-binding proteins and procaryotic proton-activated ion channels (ELIC and GLIC) enable us to model the ligand binding and activation mechanism of ligand-gated pentameric ion channels. Common versus distinct features can be deduced from the binding of agonists, antagonists and allosteric modulators in subunit interfaces of nicotinic acetylcholine, A-type gamma-aminobutyric acid, glycine and 5-HT(3)-type serotonin receptors. Ligand interactions in subunit interfaces elicit conformational waves from the closure of the agonist-binding cavity through binding loops, beta-strands and transmembrane helices to pore gating.