Mutant conductivity. (A) Single-channel cation conductance profiles calculated from 140-ns constant voltage simulations (V = ±800, 1,200 mV) from the reduced model CLDN15^WT, CLDN15^D55E, and CLDN15^D55N systems at 100 mM cation concentration. Two replicas were simulated to reduce statistical variation. (B) Snapshots of CLDN15 WT, D55E, and D55N channels taken from simulations. D64 (yellow), D55 (purple), and Na⁺ (red) are shown.