Charged Residues in the β2 Subunit Involved in GABAA Receptor Activation

Fast synaptic inhibition in the mammalian central nervous system is mediated primarily via activation of the γ-aminobutyric acid type A receptor (GABAA-R). Upon agonist binding, the receptor undergoes a structural transition from the closed to the open state. This transition, known as gating, is thought to be associated with a sequence of conformational changes originating at the agonist-binding site, ultimately resulting in opening of the channel. Using site-directed mutagenesis and several different GABAA-R agonists, we identified a number of highly conserved charged residues in the GABAA-R β2 subunit that appear to be involved in receptor activation. We then used charge reversal double mutants and disulfide trapping to investigate the interactions between these flexible loops within the β2 subunit. The results suggest that interactions between an acidic residue in loop 7 (Asp146) and a basic residue in pre-transmembrane domain-1 (Lys215) are involved in coupling agonist binding to channel gating.