Orai1 current activated by constitutively active STIM1 mutants shows minimal SCDI and is not affected by SARAF. HEK cells were transfected with Orai1 and STIM1(4E/4A) or STIM1(D76A) and with or without SARAF. The mean traces of store-independent Ca²⁺ influx (a) and the Orai1 current (b). The results in a and b are given as mean ± SEM of 30–40 cells (a) or the number of cells indicated in parentheses (b). SCDI of Orai1 activated by STIM1(4E/4A) and STIM1(D76A) is minimal and SARAF does not inhibit the Orai1-dependent Ca²⁺ influx and does not affect the SCDI. (c and d) Coimmunoprecipitation of STIM1, the STIM1 deletion mutants Δ447–460, Δ475–490, and Δ448–521, STIM1(233–535), and their 4K/4A and 4E/4A mutants with SARAF. Note that both the 4K/4A and 4E/4A mutants markedly reduce interaction of SARAF with STIM1 and constructs.