Hessing M, van 't Veer C, Hackeng T M, Bouma B N, Iwanaga S
Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.
FEBS Lett. 1990 Oct 1;271(1-2):131-6. doi: 10.1016/0014-5793(90)80389-z.
The human regulatory complement component C4b-binding protein (C4BP) is a multimeric plasma protein, which regulates the classical pathway of the complement system. C4BP functions as a cofactor to factor 1 in the degradation of C4b and accelerates the decay rate of the C4b2a complex. Previously, we have demonstrated that monoclonal antibodies (C4-2 and 9) directed against the alpha'-chain of C4b inhibit the binding of C4b to C4BP. In order to identify the structural domain of C4b that binds C4BP, proteolytic fragments of C4 were generated with trypsin and Staphylococcus aureus V8 protease. Sodium dodecyl sulfate polyacrylamide gel electrophoresis, immunoblotting and amino acid sequence analysis of the proteolytic fragments reactive with the anti-C4 mAb's revealed that the residues Ala738-Arg826 of the alpha 3-fragment of C4b are important for the interaction with C4BP.
人类调节性补体成分C4b结合蛋白（C4BP）是一种多聚体血浆蛋白，可调节补体系统的经典途径。C4BP作为因子I在C4b降解中的辅因子发挥作用，并加速C4b2a复合物的衰变率。此前，我们已经证明，针对C4bα'-链的单克隆抗体（C4-2和9）可抑制C4b与C4BP的结合。为了确定C4b与C4BP结合的结构域，用胰蛋白酶和金黄色葡萄球菌V8蛋白酶产生了C4的蛋白水解片段。对与抗C4单克隆抗体反应的蛋白水解片段进行十二烷基硫酸钠聚丙烯酰胺凝胶电泳、免疫印迹和氨基酸序列分析，结果显示，C4bα3片段的Ala738-Arg826残基对于与C4BP的相互作用很重要。
