【摘要】 用Pb2+选择电极法首次测定了CaM与Pb2+的结合常数,结果说明:Pb2+在CaM中约有10个结合位点,与文献报道的一致。其中包括4个强结合位点,结合常数在107量级,对应于Pb2+在CaM中的4个主结合位点;而其余的位点则结合常数较低,对应于Pb2+在CaM中的约6个辅助结合位点。逐级结合常数分别为:K1=2.62×107,K2=3.75×107,K3=1.03×107,K4=1.85×107,K5=2.53×106,K6=8.07×105,K7=3.36×105,K8=2.76×105,K9=2.22×105,K10=3.96×104。由于Pb2+与CaM的4个主结合位点的稳定常数比相应Ca2+的强几十到几百倍,因此Pb2+对Ca2+与CaM的竞争结合作用能够调节CaM的功能。更多还原

【Abstract】 This paper reports the measurement of the successive binding constants of Pb2+ to arabidopsis CaM(isoform Ⅱ) by using Pb2+-ion selective electrode(Pb-ISE) combined with the Excel calculation program.The Scatchard plot of Pb2+-CaM shows that there are about 4 stronger binding sites and about 6 weak binding sites of Pb2+ in CaM.This is in agreement with the literature reports.The successive binding constants for the Pb2+-CaM system are: K1=2.62×107,K2=3.75×107,K3=1.03×107,K4=1.85×107,K5=2.53×106,K6=8.07×105,K7=3.36×105,K8=2.76×105,K9=2.22×105,and K10=3.96×104.The data show that the stronger binding constants for Pb2+ to CaM are higher 1-2 order than those of Ca2+ to CaM(gerenally,106 to 105 orders).This result is benefit to the further quantitative understanding of Pb2+-Ca2+ antagonism in CaM as well as its influence on CaM′s function.更多还原