FIGURE 1.

Orai1 is the pore-forming subunit of the CRAC channel. A-D, time course and I-V curves in representative cells overexpressing wild-type STIM1 and Orai1. A, inward CRAC-like current at -100 mV. Ca²⁺-free internal solution. Solution exchanges are indicated. B, I-V curves for indicated external solutions. C, time course of current in divalent-free Na⁺ or Cs⁺ external solutions. Note absence of depotentiation for Na⁺ current and much smaller current in Cs⁺ external solution. D, I-V curves in divalent-free Na⁺ or Cs⁺ external solutions. E-H, corresponding time course and I-V curves in representative cells overexpressing wild-type STIM1 and Orai1 E106D mutant.