GABA-A-R beta 3 (GABA-A receptor subunit beta 3; also GABR3) is a 53 - 58 kDa member of the ligand-gated ion channel family of proteins. It is generally one of three beta-type subunits that contribute to a GABA-binding pentameric, postsynaptic chloride ion channel on neurons. Alternatively, it can apparently form a homopentameric channel that does not respond to GABA.
Mature human GABA-A-R beta 3 is 448 amino acids (aa) in length. It is a 4-transmembrane glycoprotein that contains an extended N-terminal extracellular region (aa 26 - 245) and a long cytoplasmic loop between aa 328 - 450. There are potential splice variants. One shows an alternate start site at Met65, while others contain either a 48 aa substitution for aa 1 - 228, a nine aa substitution for aa 1 - 80, or a 26 aa substitution for aa 1 - 26. Over aa 26 - 245, human and mouse GABA-A-R beta 3 are absolutely identical in aa sequence.