Nagasawa S, Mizuguchi K, Ichihara C, Koyama J
J Biochem. 1982 Oct;92(4):1329-32. doi: 10.1093/oxfordjournals.jbchem.a134052.
Human C4 binding protein (C4bp), which is a macromolecular weight (Mr 450,000-590,000) cofactor of C3b/C4b inactivator (I), is composed of 6 or 8 disulfide-linked polypeptide chains of Mr 75,000. Chymotrypsin cleaved C4bp into two major fragments; a large fragment of Mr 160,000, which contained carbohydrate chains and was composed of disulfide-linked polypeptide chains of Mr 25,000, and a small fragment of Mr 48,000, which was a single polypeptide chain and had the cofactor activity of C4bp. These results suggest that chymotrypsin liberates a functional domain-containing Mr 48,000 fragment from each subunit chain of C4bp and yields a core fragment derived from a disulfide-knot domain connecting each subunit chain of C4bp.
人C4结合蛋白（C4bp）是C3b/C4b灭活因子（I）的高分子量（Mr 450,000 - 590,000）辅助因子，由6条或8条Mr 75,000的二硫键连接的多肽链组成。胰凝乳蛋白酶将C4bp裂解为两个主要片段；一个Mr 160,000的大片段，其含有糖链，由Mr 25,000的二硫键连接的多肽链组成，以及一个Mr 48,000的小片段，其为单条多肽链且具有C4bp的辅助因子活性。这些结果表明，胰凝乳蛋白酶从C4bp的每个亚基链中释放出一个含功能域的Mr 48,000片段，并产生一个源自连接C4bp每个亚基链的二硫键结域的核心片段。
