Nickells M W, Atkinson J P
Howard Hughes Medical Institute Laboratories, Washington University School of Medicine, St. Louis, MO 63110.
J Immunol. 1990 Jun 1;144(11):4262-8.
We have identified and characterized C3b binding proteins of two primates, orangutan (Pongo pygmaeus) and gorilla (Gorilla gorilla). Detergent solubilized 125I surface-labeled E and PBMC were subjected to affinity chromatography with homologous or human iC3/C3b. These ligands bound a 225,000 single chain protein from orangutan E and PBMC and a 220,000 protein from gorilla E. Proteins of the same Mr were immunoprecipitated by a rabbit polyclonal and two murine mAb to the human CR1 (CD35). The C3b binding protein of gorilla E aligned with that of the common human CR1 polymorphic size variant. Human or orangutan iC3 was also a ligand for a surface-labeled protein doublet of 59,000 and 65,000 from orangutan E. The doublet pattern and mol wts are similar to membrane cofactor protein (or CD46). Further, this doublet was immunoprecipitated by a mAb to human MCP. The MCP-like protein doublet was not isolated from gorilla or human E. Decay accelerating factor (DAF) of orangutan E was also identified and was structurally and antigenically distinct from the MCP-like protein. Orangutan or gorilla E preparations were a cofactor for the cleavage of human iC3 by human factor I and produced the same cleavage fragments as human CR1. Cofactor activity of orangutan E was partially inhibited by preclearance of CR1 and more completely inhibited by preclearance of MCP. Cofactor activity of gorilla E was inhibited by coincubation with a monoclonal antibody to human CR1. These data indicate that the orangutan and gorilla high m.w. proteins are equivalent to human CR1. The orangutan E membrane protein doublet with m.w. of 59,000 and 65,000 possesses biochemical, antigenic, and functional properties of human membrane cofactor protein.
我们已经鉴定并表征了两种灵长类动物（红毛猩猩和大猩猩）的C3b结合蛋白。用去污剂溶解的125I表面标记的红细胞（E）和外周血单核细胞（PBMC）与同源或人iC3/C3b进行亲和层析。这些配体结合了来自红毛猩猩E和PBMC的225,000单链蛋白以及来自大猩猩E的220,000蛋白。相同分子量的蛋白被兔多克隆抗体和两种抗人CR1（CD35）的鼠单克隆抗体免疫沉淀。大猩猩E的C3b结合蛋白与常见的人CR1多态性大小变体的蛋白一致。人或红毛猩猩iC3也是来自红毛猩猩E的59,000和65,000表面标记蛋白双峰的配体。该双峰模式和分子量与人膜辅因子蛋白（或CD46）相似。此外，该双峰被抗人MCP的单克隆抗体免疫沉淀。未从大猩猩或人E中分离出MCP样蛋白双峰。还鉴定了红毛猩猩E的衰变加速因子（DAF），其在结构和抗原性上与MCP样蛋白不同。红毛猩猩或大猩猩E制剂是人因子I切割人iC3的辅因子，并产生与人CR1相同的切割片段。红毛猩猩E的辅因子活性被CR1的预清除部分抑制，被MCP的预清除更完全地抑制。大猩猩E的辅因子活性通过与人CR1单克隆抗体共孵育而被抑制。这些数据表明，红毛猩猩和大猩猩的高分子量蛋白等同于人类CR1。分子量为59,000和65,000的红毛猩猩E膜蛋白双峰具有人膜辅因子蛋白的生化、抗原和功能特性。
