107C in TM1 can form a multi-liganded Cd²⁺-binding site with either 337C or 338C from TM6. (A and B) Recovery of Cd²⁺-induced inhibition of 107C/337C (A) and 107C/338C (B) whole-cell currents is dramatically accelerated by DTT. (C) Summary of cadmium’s inhibitory effects on 107C, 337C, 338C, 107C/337C, and 107C/338C currents. Mean ± SEM is shown.