Résumé
The GABA(B) receptor is quite original within the large G protein-coupled receptor (GPCR) family. When first identified at the molecular level, it was the only GPCR to require two subunits to form a functional receptor, composed of GABA(B1) and GABA(B2). Although part of the mandatory dimeric class C group of GPCRs that also includes the receptors activated by glutamate, calcium, the sweet and umami taste compounds, the GABA(B) is unique in that it lacks an essential element, the cysteine-rich domain that interconnects the ligand binding domain to the heptahelical transmembrane domain (7TM) responsible for G protein activation. Here, we will summarize our actual knowledge on the structure, stoichiometry, allosteric properties, and activation mechanism. These reveal some similarities and major differences with the other class C GPCRs and highlight novel possibilities to develop approaches to regulate its activity.