CRAC channel CDI phenotypes for mutations at Orai1 position Y80. All currents were recorded in HEK293H cells cotransfected with WT mCh-STIM1 and WT or mutant Orai1-GFP after induction of I_CRAC reached a maximum (∼300 s after break-in). The representative currents shown were recorded in 20 mM Ca²⁺_o during 200-ms hyperpolarizations to the voltages indicated for WT Orai1 (A). Substitutions included Y80A (B), Y80F (C), Y80W (D), Y80E (E), and Y80K (F), with the extent of CDI for this series summarized in G. Current traces were fit to the biexponential function I = I_o + A₁e^-t/τ1 + A₂e^-t/τ2, where τ1 and τ2 represent fast and slow time constants of inactivation. Fast (H) and slow (I) time constants from biexponential fits are plotted against test potential; amplitudes of fast and slow components are shown in Fig. S3 (A and B). Each point on the summary graphs represents the mean ± SEM for n = 4–7 cells. Representative currents for additional mutations on the summary graphs are shown in Fig. S2.