Effect of Cd²⁺ on double mutant 102C/344C resembles that on 344C single mutant. (A) Inhibition of 344C currents by Cd²⁺ and slow but discernable recovery from inhibition by Cd²⁺ washout. Note that DTT could speed up the recovery process. Current relaxations were fitted with a single exponential function (red and blue solid curves), yielding the corresponding time constants, τ. (B) Inhibition of 102C/344C currents by 50 µM Cd²⁺. The current relaxation after removal of Cd²⁺ was fitted with a single exponential function (red curve), which yielded a similar time constant as that in the first part in A. (C) Effects of DTT on the current recovery from Cd²⁺-induced inhibition of 102C/344C. In contrast to the recovery phase in the absence of DTT (B), the relaxation time constant generated by the single exponential fitting (blue curve) is much shorter. (D) Effects of 50 µM Cd²⁺ on 102C. (E) Summary of current relaxation time constants for 344C and 102C/344C in the presence or absence of DTT. In both constructs, DTT significantly (P < 0.005) decreases τ. Although the relaxation time constants for 102C/344C are slightly smaller than those of 344C, the differences are not statistically significant (P > 0.1). Data shown in this figure are from inside-out patches. Mean ± SEM is shown.