Fig. 2.

(A) Secondary structure motifs and globular fold of STIM2 EF-SAM. Motif color is consistent with Fig. 1A. The Ca²⁺ ion is shown as a yellow sphere. (B) Electrostatic surface potential of STIM2 EF-SAM at neutral pH. Basic potential is shown in blue, while acidic charge is in red. (C) Comparison of the EF-hand cleft hydrophobicity for STIM2 (teal) and STIM1 (gray). The hydrophobic clefts are shaded in yellow. The Lys103 and Trp128 which contribute to the cleft in STIM2 are shown in red, while the aligned residues in STIM1 are colored in blue. (D) Orientation of the EF-hand domains relative to the SAM domains in STIM1 and STIM2. The long axes of the helices (i.e., α2 and α10) used for the interhelical angle calculations are indicated. The STIM2 and STIM1 EF-SAM pdbIDs are 2L5Y and 2K60, respectively.