Sim E, Cross S J
Biochem J. 1986 Nov 1;239(3):763-7. doi: 10.1042/bj2390763.
The plasma complement protein C4 is encoded at two highly polymorphic loci, A and B, within the class-III region of the major histocompatibility complex. At least 34 different polymorphic variants of human C4 have been identified, including non-expressed or 'null' alleles. The main method of identification of C4 polymorphic allotypes is separation on the basis of charge by agarose-gel electrophoresis of plasma. On staining by immunofixation with anti-C4 antibodies, each C4 type gives three major bands, but, since individuals can have up to five allotypes, the overlapping banding pattern is difficult to interpret. We show that digestion of plasma samples with carboxypeptidase B, which removes C-terminal basic amino acids, before electrophoresis, produces a single, sharp, distinct band for each allotype and allows identification of the biochemical basis of the multiple banding pattern previously observed in C4 phenotype determination.
血浆补体蛋白C4由主要组织相容性复合体III类区域内的两个高度多态性位点A和B编码。已鉴定出至少34种不同的人类C4多态性变体，包括非表达或“无效”等位基因。鉴定C4多态性同种异型的主要方法是通过血浆的琼脂糖凝胶电泳根据电荷进行分离。用抗C4抗体进行免疫固定染色时，每种C4类型会产生三条主要条带，但是，由于个体最多可以有五种同种异型，重叠的条带模式难以解释。我们表明，在电泳前用羧肽酶B消化血浆样品，去除C末端碱性氨基酸，每种同种异型会产生一条单一、清晰、独特的条带，并能够确定先前在C4表型测定中观察到的多条带模式的生化基础。
