Enables AP-2 adaptor complex binding activity; GABA-A receptor activity; and chloride channel activity. Involved in GABAergic synaptic transmission. Located in inhibitory synapse; plasma membrane; and terminal bouton. Is active in GABA-ergic synapse. Is integral component of postsynaptic specialization membrane. Human ortholog(s) of this gene implicated in childhood absence epilepsy and developmental and epileptic encephalopathy 43. Orthologous to human GABRB3 (gamma-aminobutyric acid type A receptor subunit beta3). [provided by Alliance of Genome Resources, Apr 2022]