Figure 4. STIM2 K-rich domain binds fully- and semi-Ca²⁺-loaded CaM in solution.

(A) Cartoon with illustration of a competition assay with GFP-STIM2K bound to Ca²⁺/CaM beads and elution of GFP–STIM2K with purified CaM from the beads. (B) Quantification of eluted GFP–STIM2K after incubation with 4 mM EGTA, 1 mM CaCl₂, and 75 μM CaM, CaM1-2m, CaM3–4m or CaM1-4m in 1 mM CaCl₂. Ca²⁺-binding EF-hand domains in the N-terminal lobe (CaM1-2m), the C-terminal lobe (CaM3-4m) or in both lobes (CaM1–4m) were mutated. Bars indicate mean±S.D. from at least three experiments (*P<0.05 and n.s. according to Student's t test).