Functional role of CRACM1-K85 mutation. Average CRAC current densities at −80 and +130 mV induced by 20 µM IP₃ in stable STIM1-expressing HEK293 cells transiently overexpressing point mutations. Black bars indicate the application of an external solution containing 50 µM 2-APB. Error bars indicate SEM. (A) Magnified plot of the initial 120-s data from B. (B) CRACM1-K85E (red; n = 6), CRACM1-K85Q (blue; n = 11), CRACM1-K85A (green; n = 10), and CRACM1-wt (black; n = 4: from a total of n = 12, four cells with the smallest current densities [induced by IP₃] were averaged to approximate the lower current density of CRACM1-K85Q). (C and D) Average I-V relationships of CRAC currents extracted from representative HEK293 cells shown in A and B and obtained at 120 s (C) and 180 s (D), when current was fully activated by 2-APB. Data represent leak-subtracted current densities (pA/pF) evoked by 50-ms voltage ramps from −150 to +150 mV.