合浦珠母贝基质蛋白KRMP-3对二价金属离子选择性的研究

用大肠杆菌表达含有GST标签的基质蛋白KRMP-3。利用圆二色谱(Circular Dichroism, CD)研究不同浓度钙离子和镁离子对基质蛋白 KRMP-3二级结构的影响。结果表明,钙离子对其二级结构的变化远大于镁离子；同时,采用荧光淬灭法研究 KRMP-3对钙,镁,锶,钡等二价金属离子的选择性,结果表明, KRMP-3对钙离子有特异性选择性,钙离子与KRMP-3的结合常数K约为103 L/mol,结合位点数 n 近似为1,表明 KRMP-3与钙离子的结合能力适中,推测基质蛋白 KRMP-3对合浦珠母贝( Pinctada fucata)棱柱层形成起到促进作用。

Ionic selectivity of KRMP-3, a shell matrix protein of Pinctada fucata

KRMP-3 with GST-tag is expressed in Escherichia coli. Using Circular dichroism (CD), we have studies the changes of KRMP-3 secondary structure with concentrations of calcium and magnesium ions, and we found that calcium ion has much stronger effect than magnesium ions. Moreover, we also studied ionic selectivity of KRMP-3 using fluorescence quenching method with Ca₂₊, Mg₂₊, Sr₂₊ and Ba₂₊, and we found that KRMP-3 has very high selectivity towards calcium ion. The static quenching constant K=10₃L/mol and the binding sites number n=1, suggesting KRMP-3 has a moderate binding capacity with calcium ion. We speculate KRMP-3 could promote the formation of the Pinctada fucata prismatic layer.