Fig. 2. Piperidine-4-sulfonic acid (P4S) has a lower efficacy at the mutant α1(L277A)β2γ2Scompared to wild-type α1β2γ2Sreceptors. P4S induced responses from individual HEK 293 cells expressing either wild-type or mutant α subunits are shown (A and B ). Bars over individual current traces indicate the duration of P4S application with the concentration of P4S in micromolars. The far right tracing represents maximal current at the same cell by applying a saturating dose of γ-aminobutyric acid (GABA). Units at the calibration bar apply to both traces (A and B ). Pooled data are plotted in concentration–effect curves (C ) for wild-type and α1(L277A)β2γ2SGABAAreceptors. The data were normalized to the maximal GABA response (300 μm). Data points shown are the means of multiple normalized experiments (table 2). Bars indicate SEM.