摘要
Calmodulin (CaM) is a multifunctional Ca 2+ binding regulatory protein with very important physiological functions. The properties of lanthanides (La 3+ ) are very similar to Ca 2+ .Their activity in living systems is usually related to competition with Ca 2+ . Therefore, the study of the interaction between lanthanides and CaM provides evidence for uncovering the functional mechanism of La 3+ in the Ca 2+ CaM enzyme system.In this report the coordination numbers and the binding sites of La 3+ on CaM were studied by using ion titration with one and two dimensional NMR. Their interactional mechanism was also discussed. After considering the effects of La 3+ on the chemical shift and on the intensity of the resonance peaks of Tyr 99, His 107 and Phe residues in 1H NMR , and after considering the effects on the correlation peaks in the 2D COSY NMR, it was concluded that the first La 3+ was bound near Tyr 99 and His 107 residues,i.e., near binding site III of Ca 2+ on CaM. This means the first La 3+ was bound the C terminal of CaM.The second and third La 3+ might have been bound on the CaM N terminal.
Calmodulin (CaM) is a multifunctional Ca 2+ binding regulatory protein with very important physiological functions. The properties of lanthanides (La 3+ ) are very similar to Ca 2+ .Their activity in living systems is usually related to competition with Ca 2+ . Therefore, the study of the interaction between lanthanides and CaM provides evidence for uncovering the functional mechanism of La 3+ in the Ca 2+ CaM enzyme system.In this report the coordination numbers and the binding sites of La 3+ on CaM were studied by using ion titration with one and two dimensional NMR. Their interactional mechanism was also discussed. After considering the effects of La 3+ on the chemical shift and on the intensity of the resonance peaks of Tyr 99, His 107 and Phe residues in 1H NMR , and after considering the effects on the correlation peaks in the 2D COSY NMR, it was concluded that the first La 3+ was bound near Tyr 99 and His 107 residues,i.e., near binding site III of Ca 2+ on CaM. This means the first La 3+ was bound the C terminal of CaM.The second and third La 3+ might have been bound on the CaM N terminal.
