Fig. 3.
For AChRs formed from unlinked subunits, mutations in both β2 and α4 subunits block NS9283 potentiation. a, b Recent cryo-EM structure of the (α4)3(β2)2 AChR (PDB code 6CNK). a Side (left) and top (right) views of the (α4)3(β2)2 AChR complex. b Left panel shows the structure of an β2–α4 subunit interface within the (α4)3(β2)2 AChR. Right panel shows a close-up view of the β2–α4 subunit interface with residues subjected to mutation, β2W176 and α4H142, highlighted as spheres. c–e Single-channel currents from wild-type or mutant (α4)3(β2)2 AChRs were recorded in the presence of 50 μM ACh and 30 μM NS9283 (holding potential − 70 mV, Gaussian filter 4 kHz). Red asterisks indicate the locations of mutations. To the right of each trace is a histogram of cluster durations, corresponding to successive channel openings and intervening closings, fitted by the sum of exponentials (dashed curves); the component with longest mean duration, present for the wild-type AChR, is reduced or absent for the mutant AChRs. To the right of the cluster duration histograms are histograms of channel openings classified as either un-potentiated (un-shaded) or potentiated (shaded) fitted by the sum of three exponentials. Above each histogram, the shaded portion of the bar indicates the percentage of channel openings that are potentiated