Fast inactivation of ORAI1 currents is diminished after deletion of CMD in cytosolic STIM1 C-terminal fragments HEK 293 as well as RBL mast cells. a and b, fast inactivation of STIM1-(233–685)- (a) and STIM1-(233–685) 7xA-mediated (b) ORAI1 Ca2+ currents upon voltage steps from a holding potential of 0 mV to −30, −50, −70, and −90 mV. c, mean fast inactivation of normalized current traces of STIM1-(233–685), -(233–685) 7xA (D/E → A, aa 475, 476, 478, 479, 481–483), -(233–685) 5xA (D/E → A, aa 478, 479, 481–483), and -(233–685) 3xA (D/E → A, aa 481–483) upon voltage steps to −90 mV. d, scheme of various STIM1 C terminus deletion mutants (233–685, 233–535, 233–485, 233–474), STIM1-(233–685) 7xA, 5xA, 3xA, and STIM1-(233–485) 7xA in comparison with the extent of inactivation of ORAI1 currents t = 90 ms (p < 0.05 for STIM1-(233–685) when compared with STIM1-(233–474), STIM1-(233–450), STIM1-(233–685) 7xA, STIM1-(233–485) 7xA), and maximum current densities). ERM, ezrin-radixin-moesin. pA, picoampere; pF, picofarad. e and f, fast inactivation of STIM1- (e) and STIM1 7xA-mediated (f) RBL CRAC currents upon voltage steps from a holding potential of 0 mV to −30, −50, −70, or −90 mV. g, mean fast inactivation of normalized current traces of e and f upon voltage steps to −90 mV (t = 90 ms, p < 0.05).