Neurotransmitter ligand-gated ion channels are transmembrane receptor-ion channel complexes that open transiently upon binding of specific ligands allowing rapid transmission of signals at chemical synapses . Five of these ion channel receptor families have been shown to form a sequence-related superfamily:
- Nicotinic acetylcholine receptor (AchR) an excitatory cation channel in vertebrates and invertebrates; in vertebrate motor endplates it is composed of alpha beta gamma and delta/epsilon subunits; in neurons it is composed of alpha and non-alpha (or beta) subunits .
- Glycine receptor an inhibitory chloride ion channel composed of alpha and beta subunits .
- Gamma-aminobutyric acid (GABA) receptor an inhibitory chloride ion channel; at least four types of subunits (alpha beta gamma and delta) are known .
- Serotonin 5HT3 receptor of which there are seven major types (5HT3-5HT7) .
- Glutamate receptor an excitatory cation channel of which at least three types have been described (kainate N-methyl-D-aspartate (NMDA) and quisqualate) .
These receptors possess a pentameric structure (made up of varying subunits) surrounding a central pore. All known sequences of subunits from neurotransmitter-gated ion-channels are structurally related. They are composed of a large extracellular glycosylated N-terminal ligand-binding domain followed by three hydrophobic transmembrane regions which form the ionic channel followed by an intracellular region of variable length. A fourth hydrophobic region is found at the C-terminal of the sequence
.This entry represents the GABA-A nicotinic glycine glutamate and 5HT3 receptors.