Studies on the mechanisms of C9 activation and of C9 inactivation by the regulatory protein(MACIF)

补体系统由20多种血清蛋白组成，在宿主防御中发挥重要作用。补体成分C9通过插入含有预先形成的C9受体C5b-8的膜，在补体级联的最后一步发挥作用。C9与C5b-8复合体相互作用后发生剧烈的构象变化。虽然已经证明了整个初级结构，但结构和功能之间的关系还没有完全理解。在这项研究中，我们试图用抗C9的单抗和化学修饰试剂DTT来阐明C9激活的机制。事实证明，1.C5b-8的结合涉及C9的两个独立的环状结构。C9的功能结构域由二硫键支撑。二硫键的不同和不同的结构域与C5b-8的结合、溶血活性和C9的自聚有关，补体功能仅针对非自体膜，而自体膜上不发生激活。补体调节蛋白(DAF、Macif、MCP、CR1)在自我决定和非自我决定中发挥重要作用。我们通过将分离的蛋白结合到影响这些蛋白的PNH红细胞上来评估DAF和Macif的功能。

The complement system consist of more than 20 serum proteins and play an important role in host defense. Complement component C9 exerts at the final step of complement cascade by inserting into membranes which contain preformed C9 acceptor, C5b-8. C9 proceeds drastic conformational changes upon interaction with C5b-8 complex. Although the entire primary structure has already been demonstrated, the structual and function relationship is not fully ubderstood. In this research, we intended to clarify the mechanisms of C9 activation by using monoclonal antibodies to C9 and also with chemical modification reagent, DTT. It has been demonstrated that1. Two seperate epoitipes of C9 are involved in C5b-8 binding.2. Functional domains of C9 are supported by disulfide bridges.3. Different and distinct domains of disulfide bridges are implicated in binding to C5b-8, hemolytic activity, and self-polymerization of C9.Complement functions are targeted only on non-self membranes, and activation does not occur on self membranes. Complement regulating proteins (DAF, MACIF, MCP, CR1) have now been demonstrated to play the crucial roles in self- and non-self determination. We have assesed the function of DAF and MACIF by inccorporating the isolated proteins to PNH erythrocytes which deffect these proteins.