Cooper N R
J Exp Med. 1973 Feb 1;137(2):451-60. doi: 10.1084/jem.137.2.451.
The role of C3 proactivator (C3PA) and a factor isolated from cobra venom (CoF) in the formation of a principle able to cleave C3 was investigated. The results clearly demonstrate two modes of interaction of C3PA with CoF. In isolated form, C3PA and CoF were found to form a reversible protein-protein complex in free solution. This complex had some C3 cleaving activity. In the presence of minute amounts of a partially purified normal serum substance, factor D, the C3PA-CoF complex was stabilized and its efficiency in cleaving C3 was greatly increased. Factor D is thus an activator of C3PA. A firm complex composed of C3PA and CoF, and possessing C3 cleaving activity, was also formed by addition of CoF to serum.
研究了C3前活化剂（C3PA）和从眼镜蛇毒中分离出的一种因子（CoF）在能够裂解C3的物质形成中的作用。结果清楚地表明了C3PA与CoF相互作用的两种模式。以分离形式存在时，发现C3PA和CoF在游离溶液中形成可逆的蛋白质-蛋白质复合物。该复合物具有一定的C3裂解活性。在存在微量部分纯化的正常血清物质D因子的情况下，C3PA-CoF复合物得以稳定，其裂解C3的效率大大提高。因此，D因子是C3PA的激活剂。通过向血清中添加CoF，也形成了由C3PA和CoF组成且具有C3裂解活性的稳定复合物。
