Figure 3. Monovalent current in the absence of divalent ions exhibits altered ion selectivity in the Orai(E180D) mutant.

a, Time course of inward current in a cell expressing wild-type Orai. Bars indicate external solution exchange. b, Same as a but for Orai(E180D). c, I–V curves for wild-type Orai at times indicated in a. d, I–V curves for Orai(E180D) at times indicated in b. e, I–V curves of Orai(E180D)-induced current in the presence of varying external [Ca²⁺]. f, [Ca²⁺] dependence of Orai(E180D) CRAC current at −130 (squares) and 90 mV (circles), scaled to the current in divalent-free solution. Ca²⁺-dependent block (mean ± s.e.m.) was fitted by the function y = 1/(1 + [Ca²⁺]/IC₅₀), where IC₅₀ is the calculated half-blocking Ca²⁺ concentration for inward current at −130 mV (48 ± 13 μM; n = 13, 8, 4, 6 and 2 cells for 20, 2, 0.2, 0.02 and 0.002 mM free external [Ca²⁺], respectively) and outward current at 90 mV (2.05 ± 0.78 mM; n = 13, 8, 4, 5 and 3 cells for 20, 2, 0.2, 0.02 and 0.002 mM free external [Ca²⁺], respectively).