Fig. 3

NMR-derived structures of Mg²⁺-bound GCAP5 (PDB entry 7M2M). (A) Ensemble of the 10 lowest-energy NMR structures. Structural statistics are listed in Table 1. (B) Average main chain structure of GCAP5 and (C) the same view rotated by 180° showing four EF-hands (colored as in Figure 1) packed in a globular arrangement very similar to what is seen for Ca²⁺-bound GCAP1.⁹ (D) Overlay of the main chain structure of GCAP5 (cyan) and the crystal structure of GCAP1 (red). The secondary structural elements are labeled as defined in Figure 1. The Ca²⁺ switch helix (α10) is colored purple. Cys15 and Cys17 side chain atoms are colored yellow. Bound Mg²⁺ is colored orange. The N-terminal myristoyl group is colored magenta. Side chain atoms of residues at the dimer interface (H18, Y21, M25, F72, and V76) and Mg²⁺ binding site (D63, D65, and D67) are indicated as sticks. (D) Overlay of main chain structures of Ca²⁺-bound GCAP1 (red) and Ca²⁺-free, Mg²⁺-bound GCAP5 (cyan).