亲和素结合蛋白性质的研究

前曾发现在日本血吸虫虫卵中，存在一种新的能与亲和素专一性结合的蛋白质，称为亲和素结合蛋白（ＡＢＰ）。在分离纯化ＡＢＰ的基础上，用ＳＤＳ－ＰＡＧＥ及ＳｅｐｈａｄｅｘＧ－１５０分别测定了ＡＢＰ的分子量，并做了糖蛋白染色及等电，大测定。实验结果表明ＡＢＰ是一个分子量为６５ｋＤ的碱性糖蛋白，由数个相同的分子量为１２．７ｋＤ的亚单位组成。ＳＤＳ、β－巯基乙醇处理的ＡＢＰ仍能与亲和素结合，提示ＡＢＰ的亚单位能与亲和素结合。氨基酸修饰剂ＮＡＩ、ＤＴＮＢ、ＮＥＭ及ＮＢＳ对ＡＢＰ与亲和素的结合有不同程度的影响，而ＨＮＢＢ、ＴＮＢＳ及ＩＡＡ对ＡＢＰ与亲和素的结合无影响，提示ＡＢＰ分子中氨基酸残基Ｔｙｒ、Ｃｙｒ是ＡＢＰ与亲和素结合所必需的，可能参与结合位点的形成。另外，测得ＡＢＰ与亲和素结合的结合常数为１．４×１０~（－７）ｍｏｌ／Ｌ。

Studies on Property of Avidin-binding Protein

We have found an Avidin-binding protein (ABP) in the eggs of Schistosoma japonicum. The molecular weight of ABP was determined by SDS-PAGE and Sephadex G-150, specific dying of glycoprotein and determination of isoelectric point were also carried out. These results showed that ABP is a 65kD glycoprotein which consisted of several subunits with M. W. of 12. 7kD. ABP treated with SDS, β-ME could still combine with avidin, and avidin treated with 0periodate could still combine with ABP. It suggests that the subunits of ABP also have combining activity and the combination is no relation to sugar chain of avidin. The results of amino acid modification showed that the amino acid Tyr and Cys are necessary for combination of ABP and avidin. The constant of combination of ABP and avidin is 1. 4 10￣(-7)M￣(-1).