Figure 3. α-helicity of STIM2 K-rich domain contributes in binding to Ca²⁺/CaM.

(A) Binding of 1 μM reduced GFP, GFP–STIM1C, GFP–STIM1C∆K, GFP–STIM2C and GFP-STIM2C∆K to Ca²⁺/CaM beads in 1 mM CaCl₂ and GFP–STIM1C and GFP-STIM2C in 1 mM EGTA. (B) Binding of 1 μM reduced GFP, GFP–STIM1K, GFP–STIM1K–P675A, GFP–STIM1K–P682A, GFP–STIM1K–P675A–P682A, GFP–STIM2K and GFP–STIM2K–K743P to Ca²⁺/CaM beads in 1 mM CaCl₂. (C) Binding of 1 μM GFP–STIM1K, GFP–STIM1K–P675A–P682A, GFP–STIM1K+LC, GFP–STIM1K+LC–P675A–P682A, GFP–STIM2K, and GFP–STIM2K–C725A (all dialysed against DTT-free buffer) to Ca²⁺/CaM beads in 1 mM CaCl₂. Bars indicate mean±S.D. from at least three experiments (*P<0.05, **P<0.005, n.s. according to Student's t test).