Fig. 5: Agonist-driven gating of β-GluCl’s pore does not require the capping of loop C.

a, b Inward currents recorded from the indicated constructs in the whole-cell patch-clamp configuration in response to 20-ms (a) or 1-min (b) exposures to pH-4.5 extracellular solution. For the “wild-type” GLIC–β-GluCl ECD–TMD chimera, responses are shown as the mean (black solid line) ± one standard deviation (SD; gray error bars) of normalized responses recorded from different whole-cell experiments. Averaged wild-type data in (a) correspond to a total of 98 responses recorded from 9 different cells, and those in (b) correspond to a total of 9 responses recorded from 9 different cells. Each individual normalized response shown for the loop-C-deleted mutant was recorded from a different cell. The pipette potential was –60 mV. c Inward currents recorded from the indicated constructs in the whole-cell patch-clamp configuration in response to 20-ms pulses of agonist. The latter was pH 4.5 for the GLIC–β-GluCl chimera; 100-μM ACh for both the α7 AChR and the α1β1δε AChR; 200-μM ACh for the α3β4 AChR; and 1-mM GABA for both heteromeric GABA_ARs. Each displayed trace is the average of several normalized responses recorded from different cells; for the sake of clarity, only the mean of each distribution is shown. The traces were horizontally aligned at their half-activation times. The chimera’s currents decay (deactivate) more slowly than those of the α7 AChR, faster than those of the ganglionic (α3β4) AChR and heteromeric GABA_ARs, and at nearly the same rate as those of the adult-type muscle (α1β1δε) AChR. The pipette potential was –60 mV. d Whole-cell currents recorded under KCl-dilution conditions (high KCl concentration in the pipette solution; low, in the extracellular solution); the pipette potentials indicated next to each trace were corrected for the liquid-junction potential that arises between these two solutions. The indicated equilibrium potentials (E_Cl^– and E_K⁺) were calculated at 22 °C using ion concentrations. The reversal potential of the chimera was very close to the equilibrium potential for Cl^– (E_Cl^–). For all panels, black dashed lines denote the zero-current baseline. Source data are provided as a Source Data file.