Farries T C, Seya T, Harrison R A, Atkinson J P
Howard Hughes Medical Institute Laboratories, Washington University School of Medicine, St. Louis, Mo.
Complement Inflamm. 1990;7(1):30-41. doi: 10.1159/000463124.
The reaction of radiolabeled C3b-binding proteins with C3b-coated particles has been investigated. CR1 binding was inhibited by factor H and factor B (in the presence of properdin), but not by properdin alone. CR2 and MCP binding were also inhibited by factor H. Therefore factor H, factor B, CR1, CR2 and MCP probably comprise a group of mutually competitive proteins with similar or overlapping binding sites on C3b. These results correlate with their structural homology and suggest that they all evolved from a single C3b-binding molecule. Factor H, CR1 and MCP are also cofactors for the factor-I-mediated cleavage of C3b. A species incompatibility between rat factor I and human CR1 for the cleavage of human C3b suggests the possibility that cofactors may also function by interacting directly with factor I.
已对放射性标记的C3b结合蛋白与C3b包被颗粒的反应进行了研究。CR1的结合受到H因子和B因子（在备解素存在的情况下）的抑制，但单独的备解素不会抑制。CR2和MCP的结合也受到H因子的抑制。因此，H因子、B因子、CR1、CR2和MCP可能构成一组在C3b上具有相似或重叠结合位点的相互竞争蛋白。这些结果与它们的结构同源性相关，并表明它们都从单个C3b结合分子进化而来。H因子、CR1和MCP也是I因子介导的C3b裂解的辅因子。大鼠I因子与人CR1在裂解人C3b方面的种属不相容性表明，辅因子也可能通过与I因子直接相互作用发挥作用。
