Stewart J L, Kolb W P, Sodetz J M
J Immunol. 1987 Sep 15;139(6):1960-4.
The aim of this study was to identify constituents of the intermediate C5b-7 complex of human complement that mediate binding of C8 and formation of C5b-8. Analysis of interactions between purified C8 and C5, C6, or C7 indicate that C5 and C8 associate to form a dimer in solution. This interaction is specific and involves a single C5 binding site located on the beta-subunit of C8. Simultaneous interaction of C8 with C5 and C9 in solution suggests that during assembly of the cytolytic C5b-9 complex on membranes, C8 binds to C5b-7 through association of beta with C5b, after which C9 associates through interaction with the previously identified C9-specific site on the alpha-subunit. Other evidence of interaction with C5b was provided by the fact that C8 can bind purified C5b6. Also, in situ cross-linking experiments showed that within C5b-8, the beta-subunit is in close proximity to C5b. These results indicate that C8 binding to C5b-7 is mediated by a specific C5b recognition site on beta, thus explaining the requirement for this subunit in C5b-8 formation. They also reveal that C5b contains a specific site for interaction with beta.
本研究的目的是确定人补体中间C5b - 7复合物中介导C8结合及C5b - 8形成的成分。对纯化的C8与C5、C6或C7之间相互作用的分析表明，C5和C8在溶液中缔合形成二聚体。这种相互作用具有特异性，涉及位于C8β亚基上的单个C5结合位点。溶液中C8与C5和C9的同时相互作用表明，在膜上细胞溶解型C5b - 9复合物组装过程中，C8通过β与C5b缔合而与C5b - 7结合，之后C9通过与α亚基上先前鉴定的C9特异性位点相互作用而缔合。C8能结合纯化的C5b6这一事实提供了与C5b相互作用的其他证据。此外，原位交联实验表明，在C5b - 8内，β亚基与C5b紧密相邻。这些结果表明，C8与C5b - 7的结合由β上的特定C5b识别位点介导，从而解释了该亚基在C5b - 8形成中的必要性。它们还揭示C5b含有与β相互作用的特定位点。
