Native GABA B receptors are heteromultimers with a family of auxiliary subunits

GABAB receptors are the G-protein-coupled receptors for γ-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the brain. Here, functional proteomics is used to show that GABAB receptors in the brain are complexes of GABAB1, GABAB2 and members of a subfamily of KCTD proteins. The KCTD proteins increase the potency of agonists and markedly alter the G-protein signalling of the receptors, suggesting that they determine the pharmacology and kinetics of the receptor response.