Fig. 2.

Channel properties of Orai1 GOF cysteine mutants. (A–F) Constitutive activity of the indicated Orai1 variants. (Top) Traces show time course of current in the absence of STIM1 following whole-cell break-in (t = 0). (Bottom) Graphs depict I–V relationships of the indicated mutants measured in 20 mM extracellular Ca²⁺ solution. (G–L) Store-operated activation of WT and mutant Orai1 channels in STIM1-coexpressing cells. In contrast to all other mutants, H134C does not show additional current increase following whole-cell break-in. (Bottom) Graphs show I–V relationships of the different mutants. Note that STIM1 coexpression shifts the reversal potential of the mutant channels in all cases (SI Appendix, Table S1).