Analysis of the functions and structures of the domains of the complement protein C2 and its role in innate immunity

The following study will elucidate in detail the characteristics of interaction between complement proteins C2 and C4. C2-C4 interaction experiments will be based on the use of recombinant wild-type or mutant C2 fragments (rC2) and native C4/C4b. C2 is a mosaic (modular) protein consisting of CCP (complement control protein), vWF (von Willebrand Factor) and SP (Serine protease) domains, and so these domains can be synthesised as recombinant proteins. In contrast C4 has no recognisable modular structure, and there is no logical basis on which to base the synthesis of recombinant segments. Therefore native C4, and its natural proteolysis products, C4b, C4c and C4d will be used. The major aims of the work are to characterise potential C4b-binding sites within the vWF domain of C2, then within the CCP and SP domains. The binding site on C4b for C2 will also be examined using proteolysis products of C4 and a panel of anti-C4 monoclonal antibodies. C4 fragments and recombinant C2 domains will also be used in crystallisation attempts, as a means of detecting their 3D structure.