ABSTRACT
This chapter examines complement control protein (CCP) modules, with an emphasis on their contribution to the structure of the following regulators of complement activation (RCA) proteins: membrane cofactor protein (MCP), the factor H family (fH), and C4b-binding protein (C4BP). Many proteins of the complement system are built up from a limited range of module types. The CCP module is very strongly represented with 69 occurrences among the most common allotypes of the five proteins that have been shown to regulate complement and belong to the RCA family: fH, C4BP, MCP, Complement receptor 1, and Decay accelerating factor. Comparative or homology-based modeling is a widely used technique for predicting 3D structure of proteins. Each RCA protein has multiple binding sites, and each binding site encompasses surface elements from two or more neighboring CCP modules. Each intermodular junction may be regarded as being made up from proximal loops and strands of the respective neighbors, plus the “linker.”.
