Figure 4: The three SOAR concatemer–dimers, YFP-S-S, YFP-SH-S and YFP-S-SH are functionally identical.

Fura-2 ratiometric Ca²⁺ responses in stable HEK-Orai1-CFP cells transiently expressing the same levels of either: (a) YFP-S-S (43 cells); (b) YFP-SH-S (50 cells); (c) YFP-S-SH (49 cells); (d) YFP-SH-SH (48 cells). Constitutive Ca²⁺ entry was measured using cells in nominally Ca²⁺-free solution, replaced with 1 mM Ca²⁺ solution (Ca²⁺). (a–d) Results are means of the cell numbers indicated±s.e.m. and are representative of three independent repeats. (e) Statistics for average peak of constitutive Ca²⁺ entry shown in a–d ,*P<0.001 from YFP-S-S; (f) statistics for Ca²⁺ entry rates shown in a–d, *P<0.001 from YFP-S-S; (g) average YFP fluorescence intensity (arbitrary fluorescence units; AFUs) of cells used in a–d). (e–g) Results are means±s.e.m. of three independent experiments. (h) I/V relationship of whole-cell I_CRAC measurements for YFP-S-S (black), YFP-SH-S (green), YFP-S-SH (red) or YFP-SH-SH (blue) transiently expressed in HEK-Orai1-CFP stable cells. Quantification of current densities for the three active concatemer–dimers are given in Supplementary Fig. 3.