A ligand-gated ion channel opens when:
Ligand-gated ion channels, also called ionotropic receptors, provide fastest chemical to electrical transduction at synapses through direct conformational coupling between binding and pore opening without second messengers. They are multimeric membrane proteins typically pentameric Cys-loop family including nicotinic acetylcholine, GABA-A, glycine and 5-HT3 receptors, or tetrameric glutamate receptors AMPA, NMDA and kainate, each with extracellular ligand-binding domain formed by loops and transmembrane pore domain of four helices M1-M4 surrounding central ion pathway. Binding of specific agon
Ref: Alberts et al., Molecular Biology of the Cell, 6th ed., Chapter 15: Ligand-Gated Ion Channels – Mechanism.
