Mustafi Sourajit M, Mukherjee Sulakshana, Chary Kandala V R, Del Bianco Cristina, Luchinat Claudio
Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai 400 005, India.
Biochemistry. 2004 Jul 27;43(29):9320-31. doi: 10.1021/bi049657d.
The displacement of Ca(2+) by trivalent lanthanide ions (Tm(3+)) in a protozoan (Entamoeba histolytica) Ca(2+) binding protein has been studied by NMR and isothermal calorimetry (ITC). The study provides a basis for understanding the behavior of lanthanides when used as a substitute for Ca(2+), the pattern of sequential binding, the structural changes involved, the range and magnitude of paramagnetic interaction, and the associated energetics and mechanism. The progressive Ca(2+) displacement from site III first, followed by displacement from site II, I, and IV, as observed during the NMR titration experiments, is interpreted in the light of ITC data to provide a deeper insight into the intradomain and, for the first time, interdomain cooperativity and information about the statistical phenomenon involved in it. A theoretical model governing Ca(2+) displacement is provided. The small structural changes involved in Ca(2+) displacement by a diamagnetic lanthanide (La(3+)) has also been monitored.
通过核磁共振（NMR）和等温滴定量热法（ITC）研究了三价镧系离子（Tm(3+)）在原生动物（溶组织内阿米巴）钙结合蛋白中对钙离子（Ca(2+)）的取代作用。该研究为理解镧系元素作为钙离子替代物时的行为、顺序结合模式、所涉及的结构变化、顺磁相互作用的范围和强度以及相关的能量学和机制提供了基础。根据ITC数据解释了在NMR滴定实验中观察到的钙离子从位点III开始逐步被取代，随后是位点II、I和IV的取代现象，以便更深入地了解结构域内以及首次了解结构域间的协同作用以及其中涉及的统计现象。提供了一个控制钙离子取代的理论模型。还监测了抗磁性镧系元素（La(3+)）取代钙离子时所涉及的微小结构变化。
