Colomb M, Porter R R
Biochem J. 1975 Feb;145(2):177-83. doi: 10.1042/bj1450177.
Rabbit immunoglobulin gamma (IgG) was digested with plasmin after being left for 15 min at pH2.5, 30 degrees C followed by a rapid increase in the pH to 7. The fragment antigen and complement binding (Facb) was isolated and characterized chemically and biologically. Sequence studies showed that the C-terminal quarter of the heavy chain had been removed, the split occurring at a lysine-alanine bond in the sequence Thr-Ile-Ser-Lys-Ala-Arg. The fragment Facb retained the capacity to precipitate with antigen and the precipitate caused activation of the first component of complement of the same order as that of acid-treated IgG. Both Facb and acid-treated IgG showed a fall in complement fixation relative to the native molecule of 30-40%.
兔免疫球蛋白γ（IgG）在pH2.5、30℃下放置15分钟后用纤溶酶消化，随后pH迅速升至7。分离出片段抗原和补体结合片段（Facb），并对其进行化学和生物学特性鉴定。序列研究表明，重链的C末端四分之一已被去除，裂解发生在序列Thr-Ile-Ser-Lys-Ala-Arg中的赖氨酸-丙氨酸键处。片段Facb保留了与抗原沉淀的能力，且沉淀物引起补体第一成分的激活，其激活程度与酸处理的IgG相同。相对于天然分子，Facb和酸处理的IgG的补体结合能力均下降了30%-40%。
