Abstract: The structural and energetic characteristics of calmodulin binding Ca²⁺, Mg²⁺, K⁺ and Na⁺ were studied by molecular dynamics method. The detailed structure and energy of the four complexes were analyzed and discussed. The results reveal the structural difference between four complexes formed by calmodulin and metal ions. K⁺ and Na⁺ can departure from the calmodulin during the simulation, which prove that both ions could not coordinate to the EF-hand motif. Although Ca²⁺ and Mg²⁺ could coordinate with calmodulin effectively, large structural changes between the holo-calmodulin and the apo-calmodulin only are observed when Ca²⁺ bind to the EF-hand motifs. The energetic analysis suggest that the interaction between the Ca²⁺ and the EF-hand motif is much stronger than that of Mg²⁺, which brings the conclusion of this work that the interaction between ions and the calmodulin dictates the final structure of the complex and further activate the protein.

Key words: Calmodulin, Molecular dynamics, Ions selectivity, Binding energy