钙调素离子选择性的理论研究

Theoretical Study on Ions Selectivity of Calmodulin

通过分子动力学模拟计算研究了Ca2+,Mg2+,K+,Na+与钙调素形成复合物的结构和能量特征.计算得到了结合不同离子后的钙调素结构差异,阐明了钙调素对这几种离子具有不同结合性质的结构和动力学原因.其中,Ca2+与钙调素EF-hand基序中侧链残基上的氧原子形成配位键,从而使其复合物的结构有较大的改变,而和Ca2+同一主族,性质相似的Mg2+及不同主族的Na+和K+,它们与钙调素的结合能力比Ca2+与钙调素的弱许多,对钙调素结构的影响也较小,由此推测钙调素与Ca2+的结合机制和钙调素对Ca2+具有选择性的原因是由离子与钙调素中EF-hand基序的结合强度和构型共同决定的.

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.