Assimeh S N, Painter R H
J Immunol. 1975 Aug;115(2):488-94.
The binding of C1 to IgG and the interactions between C1 subcomponents have been studied by affinity chromatography of serum C1 and purified C1 proteins on Sepharose-IgG. Affinity chromatography of serum on Sepharose-IgG resulted in the binding of C1; subsequent washing with EDTA removed only C1s and C1t. Affinity chromatography of serum-EDTA on Sepharose-IgG resulted in binding of only C1q and C1r. Affinity chromatography of serum on Sepharose-tryptophan-modified-IgG resulted in the binding of only C1r and C1s. By the use of purified C1 proteins and Sepharose-IgG in binding studies it was confirmed that both C1q and C1r bind independently to sites on IgG and hold C1s and C1t by Ca++-dependent bonds. Measurements of the hemolytic activity of various combinations of C1 subcomponents confirmed the data obtained by the affinity binding studies. Both C1t and C1r independently enhanced the C1 activity of C1q-C1s mixtures; maximal activity required all four subcomponents. Sucrose gradient ultracentrifugation of mixtures of C1 proteins showed formation of the following complexes: C1qs (12S), C1qrs (15S), C1qst (18-23S), and C1qrst (19S). The evidence suggests that the spatial sequence of the components of the Sepharose-IgG-Serum C1 complex is: Sepharose-IgG: C1q: C1t: C1s: C1r: IgG-Sepharose. The probable physiologic significance of this model is discussed.
通过血清C1和纯化的C1蛋白在琼脂糖-免疫球蛋白G（Sepharose-IgG）上的亲和层析，研究了C1与免疫球蛋白G（IgG）的结合以及C1亚组分之间的相互作用。血清在Sepharose-IgG上进行亲和层析导致C1结合；随后用乙二胺四乙酸（EDTA）洗涤仅去除C1s和C1t。血清-EDTA在Sepharose-IgG上进行亲和层析仅导致C1q和C1r结合。血清在色氨酸修饰的琼脂糖-免疫球蛋白G（Sepharose-tryptophan-modified-IgG）上进行亲和层析仅导致C1r和C1s结合。在结合研究中使用纯化的C1蛋白和Sepharose-IgG证实，C1q和C1r均独立结合至IgG上的位点，并通过钙离子依赖性键保持C1s和C1t。对C1亚组分各种组合的溶血活性测量证实了通过亲和结合研究获得的数据。C1t和C1r均独立增强C1q-C1s混合物的C1活性；最大活性需要所有四个亚组分。C1蛋白混合物的蔗糖梯度超速离心显示形成以下复合物：C1qs（12S）、Cqrs（15S）、C1qst（18 - 23S）和C1qrst（19S）。证据表明Sepharose-IgG - 血清C1复合物各组分的空间序列为：Sepharose-IgG:C1q:C1t:C1s:C1r:IgG-Sepharose。讨论了该模型可能的生理意义。
