An intracellular residue, D933, influences TRPM2 channel gating. (A) Current amplitude measured at +100 and −100 mV of D933E, D933N, D933H, D933K, and D933A compared with WT TRPM2. The mutant channels were activated by intracellular solutions containing 100 µM Ca²⁺ and 1 mM ADPR, whereas WT TRPM2 was activated by 100 nM Ca²⁺/200 µM ADPR. Note that D933E and D933N quickly inactivated after activation. (B) Mean current amplitude of WT TRPM2 and the mutants recorded with 100 nM Ca²⁺/200 µM ADPR. (C) Mean current amplitude of the mutants activated by 100 µM Ca²⁺/1 mM ADPR. (D–I) I-V relationship of D933N, D933E, D933H, D933K, and D933A compared with that of WT TRPM2. Both D933E and D933H displayed smaller inward currents than that of D933N.