Kerr M A, Porter R R
Biochem J. 1978 Apr 1;171(1):99-107. doi: 10.1042/bj1710099.
The second component of human complement (C2) was purified by a combination of euglobulin precipitation, ion-exchange chromatography, (NH4)2SO4 precipitation and affinity chromatography. The final product was homogeneous by the criterion of polyacrylamide-gel electrophoresis and represents a purification of about 4000-fold from serum with 15-20% yield. Component C2 comprises a single carbohydrate-containing polypeptide chain, with an apparent mol.wt. of 102000; alanine is the N-terminal amino acid. The molecule is rapidly cleaved by activated subcomponent C1s with the loss of haemolytic activity to yield two fragments with apparent mol.wts. of 74000 and 34000. These fragments are not linked by disulphide bonds and can be easily separated. A second protein isolated during the purification of component C2 was identified by its haemolytic and antigenic properties as complement Factor B, the protein serving an analogous function to component C2 in the alternative pathway. The protein, which is also a single carbohydrate-containing polypeptide chain, has an apparent mol.wt. of 95000 and threonine as N-terminal amino acid. The amino acid analyses of component C2 and Factor B are compared.
人补体的第二个成分（C2）通过优球蛋白沉淀、离子交换色谱、硫酸铵沉淀和亲和色谱相结合的方法进行纯化。根据聚丙烯酰胺凝胶电泳的标准，最终产物是均一的，从血清中纯化约4000倍，产率为15%-20%。C2成分包含一条含单一碳水化合物的多肽链，表观分子量为102000；丙氨酸是N端氨基酸。该分子被活化的亚成分C1s迅速裂解，溶血活性丧失，产生两个表观分子量分别为74000和34000的片段。这些片段不以二硫键相连，很容易分离。在纯化C2成分过程中分离出的第二种蛋白质，根据其溶血和抗原特性被鉴定为补体因子B，该蛋白质在替代途径中起与C2成分类似的作用。该蛋白质也是一条含单一碳水化合物的多肽链，表观分子量为95000，苏氨酸为N端氨基酸。对C2成分和因子B的氨基酸分析进行了比较。
