Glycine receptors are members of the ligand-gated ion channel superfamily, which mediate fast inhibitory neurotransmission. The receptors are pentameric membrane proteins which form chloride channels. Binding of glycine to its receptor produces an increase in chloride conductance and membrane hyperpolarisation. Four genes encoding glycine receptor alpha subunits have been identified, together with a single beta polypeptide. Each subunit consists of a large extracellular N-terminal region, four transmembrane domains, and a large cytoplasmic domain.