Fig. 5: A non-canonical serine in the Q/R/N site of GluE1αA contributes to non-selective monovalent currents and weak rectification indicative of reduced polyamine block.

a Sample wildtype GluE1αA whole-cell currents elicited by 3 mM glycine recorded at membrane voltages ranging from −80 mV to +80 mV under bi-ionic conditions of 150 mM intracellular Na⁺ and 150 mM extracellular X⁺ ions where X is Na, Li, K or Cs. b Plot of average normalized current vs. membrane voltages (I-V) under equimolar intracellular and extracellular Na⁺ conducted by wildtype and pore mutant variants of GluE1αA, the wildtype human GluA2 receptor, and a mutant GluA2 variant bearing a glutamine (Q) to serine (S) mutation in the pore Q/R/N site (n = 6–13). c Similar I-V plot as b but with equimolar internal Na⁺ and external Li⁺ (n = 6–9). d I-V graph with equimolar internal Na⁺ and external K⁺ (n = 7–10). e I-V plot with equimolar internal Na⁺ and external Cs⁺ (n = 6–9). f Average permeability ratios (pX⁺/pNa⁺) ± standard deviation calculated from the I-V data presented in b to e. g Average normalized conductance vs. membrane voltage (G-V) plot derived from the I-V data in b for the different receptors and variants under symmetric bi-ionic Na⁺ conditions. Inset: plot of differences in the normalized conductance data for all receptor variants relative to their wildtype counter parts at 0 mV (i.e., values demarked by the green dashed box in the main plot). Differences between average wildtype and corresponding variant conductance data at 0 mV were all significant in paired T-tests (p ≤ 5.5E−6). The legend embedded in b pertains to b to e and g.