Ca2+ binding sites in calmodulin and troponin C alter interhelical angle movements

Molecular dynamics analyses were performed to examine conformational changes in the C-domain of calmodulin and the N-domain of troponin C induced by binding of Ca2+ ions. Analyses of conformational changes in calmodulin and troponin C indicated that the shortening of the distance between Ca2+ ions and Ca2+ binding sites of helices caused widening of the distance between Ca2+ binding sites of helices on opposite sides, while the hydrophobic side chains in the center of helices hardly moved due to their steric hindrance. This conformational change acts as the clothespin mechanism. (C) 2004 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.