Fearon D T, Austen K F, Ruddy S
J Exp Med. 1974 Aug 1;140(2):426-36. doi: 10.1084/jem.140.2.426.
The protein in the properdin pathway responsible for conversion of precursor factor D to D has been isolated and found to be identical with properdin. Sequential ion exchange and gel filtration chromatography demonstrated identity between properdin protein, measured by radial immunodiffusion, and the capacity to activate D to D, assessed by formation of the intermediate, EAC43B(D). Properdin, purified in this manner, was homogeneous on acid polyacrylamide disc gel electrophoretic analysis, with the band of protein corresponding to the position of eluates in the replicate gel capable of activating highly purified D. Demonstration of the homogeneity of purified D by alkaline disc gel electrophoresis, coupled with the linear stoichiometric hemolytic titrations of each factor, indicates that direct interaction between properdin and D generates D. Thus, activation of D by properdin represents a mechanism in the properdin pathway by which D becomes available for formation of the C3b-dependent C3 convertase.
备解素途径中负责将前体因子D转化为因子D的蛋白质已被分离出来，发现其与备解素相同。通过连续离子交换和凝胶过滤色谱法表明，用放射免疫扩散法测定的备解素蛋白与通过形成中间体EAC43B（D）评估的激活因子D转化为因子D的能力相同。以这种方式纯化的备解素在酸性聚丙烯酰胺圆盘凝胶电泳分析中是均一的，蛋白质条带与复性凝胶中能够激活高度纯化的因子D的洗脱液位置相对应。通过碱性圆盘凝胶电泳证明纯化的因子D的均一性，再结合每个因子的线性化学计量溶血滴定，表明备解素与因子D之间的直接相互作用产生了因子D。因此，备解素对因子D的激活代表了备解素途径中的一种机制，通过该机制因子D可用于形成C3b依赖性C3转化酶。
