The role of C4-binding protein and {beta }1H in proteolysis of C4b and C3b
The role of C4-binding protein and {beta }1H in proteolysis of C4b and C3b
复制标题
C4结合蛋白和{β}1H在C4b和C3b蛋白水解中的作用
DOI：
--
复制
发表时间：
1979
影响因子：
15.3
通讯作者：
J. E. Men
中科院分区：
文献类型：
--
作者：
Teizo Fujita;Victor Nussenzweig;J. E. Men
用离子交换层析分离了两种形式的C4结合蛋白(C4-BP)(C4-BP低，C4-BP高)，用离子交换层析分离了两种形式的C4结合蛋白(C4-BP低，C4-BP高)。这两种形式的C4-BP都是C3b在溶液中被C3b钝化剂裂解的辅助因子，所产生的C4b的a‘链片段具有相同的分子质量。此外，与β1H类似，C4-BP的低或高是C3bINA裂解液相C3b的辅助因素。然而，在C4-BP和β1H活性之间观察到了重要的数量差异。对于溶液中的C3b，β1H的辅因子活性约等于C4-BP重量的20倍。与细胞结合的C3b相比，活性的差异更加明显。而β1H可增强C3bINA对红细胞中间体EC3b的作用，抑制EC3bBb的聚集，而C4-BP在浓度约等于β1H的300倍时也不起作用。因此，在生理条件下，β1H很可能是控制C3b功能的关键蛋白，而C4-BP活性主要针对C4b的切割。我们还研究了C4-BP与Stroud和合作者(3，4)所描述的C3b-C4bINA辅因子之间的关系。从功能、理化和免疫学标准来看，它们是相同的蛋白质。
Two forms of C4-binding protein (C4-bp) (C4-bp low, C4-bp high), which differ slightly in net charge and apparent molecular weight, as determined by SDS- PAGE, were separated by ion-exchange chromatography and contaminants removed with specific antisera. Both forms of C4-bp served as cofactors for the cleavage of C4b in solution by C3b inactivator, and the resulting fragments of the a’-chain of C4b had identical molecular weights. In addition, similarly to β1H, C4-bp low or high served as cofactors for the cleavage of fluid phase C3b by C3bINA. However, important quantitative differences between the activities of C4-bp and β1H were observed. With regard to C3b in solution, the cofactor activity of β1H was {approximately equal to}20 times greater than that of C4-bp on a weight basis. In relation to cell-bound C3b, the differences in activity were even more marked. Whereas β1H enhanced the effects of C3bINA on the erythrocyte intermediate EC3b, inhibiting the assembly of EC3bBb, C4-bp was without effect even at concentrations {approximately equal to}300 times greater than β1H. Therefore, under physiological conditions, it is likely that β1H is the key protein which controls the function of C3b, and that C4-bp activity is directed mainly toward the cleavage of C4b. We also examined the relation between C4-bp and the C3b-C4bINA cofactor described by Stroud and collaborators (3, 4). By functional, physico-chemical and immunological criteria, they are the same protein.