Gamma-aminobutyric acid A receptor/Glycine receptor alpha (IPR006028)

Short name: GABAA/Glycine_rcpt

Overlapping homologous superfamilies


Family relationships


Gamma-aminobutyric acid type A (GABAA) receptors are members of the neurotransmitter ligand-gated ion channels: they mediate neuronal inhibition on binding GABA. The effects of GABA on GABAA receptors are modulated by a range of therapeutically important drugs, including barbiturates, anaesthetics and benzodiazepines (BZs) [PMID: 8537206]. The BZs are a diverse range of compounds, including widely prescribed drugs, such as librium and valium, and their interaction with GABAA receptors provides the most potent pharmacological means of distinguishing different GABAA receptor subtypes.

GABAA receptors are pentameric membrane proteins that operate GABA-gated chloride channels [PMID: 11282419]. Eight types of receptor subunit have been cloned, with multiple subtypes within some classes: alpha 1-6, beta 1-4, gamma 1-4, delta, epsilon, pi, rho 1-3 and theta [PMID: 9647870, PMID: 10449790]. Subunits are typically 50-60kDa in size and comprise a long N-terminal extracellular domain, containing a putative signal peptide and a disulphide-bonded beta structural loop; 4 putative transmembrane (TM) domains; and a large cytoplasmic loop connecting the third and fourth TM domains. Amongst family members, the large cytoplasmic loop displays the most divergence in terms of primary structure, the TM domains showing the highest level of sequence conservation [PMID: 2538761].

Most GABAA receptors contain one type of alpha and beta subunit, and a single gamma polypeptide in a ratio of 2:2:1 [PMID: 11712530], though in some cases other subunits such as epsilon or delta may replace gamma. The BZ binding site is located at the interface of adjacent alpha and gamma subunits; therefore, the type of alpha and gamma subunits present is instrumental in determining BZ selectivity and sensitivity. Receptors can be categorised into 3 groups based on their alpha subunit content and, hence, sensitivity to BZs: alpha 1-containing receptors have greatest sensitivity towards BZs (type I); alpha 2, 3 and 5-containing receptors have similar but distinguishable properties (type II); and alpha 4- and 6-containing assemblies have very low BZ affinity [PMID: 11712530]. A conserved histidine residue in the alpha subunit of type I and II receptors is believed to be responsible for BZ affinity [PMID: 11712530].

This entry also includes glycine receptor subunit alpha [PMID: 23038260] and subunits of the acetylcholine-gated chloride channel (ACC) in the nematode Caenorhabditis elegans. ACC is a heteropentamer consisting of ACC-1 and ACC-3, ACC-1 and ACC-4, ACC-2 and ACC-3 or ACC-2 and ACC-4. It is triggered in response to acetylcholine, but not GABA, glutamate, glycine, histamine or dopamine [PMID: 15579462].

GO terms

Biological Process

GO:0034220 ion transmembrane transport

Molecular Function

GO:0005216 ion channel activity
GO:0004888 transmembrane signaling receptor activity

Cellular Component

GO:0016021 integral component of membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.