Schematic illustration of binding sites on C4BPβ+ for different ligands. Several ligands bind C4BP, most of them to the α chains. It should be noted that while the binding sites are shown on a single chain, these will be replicated on all the other α chains. C4b and LRP bind to CCP1-3. C3b binds to either CCP1-4 or CCP1-5 (see “C4b-binding protein”). The pathogens S pyogenes and B pertussis bind to CCP1-2 and E coli OmpA binds to CCP3. Different coat proteins of N gonorrhoeae bind to different regions of C4BP; pili binds to CCP1-2, whereas Por IA and Por IB bind to CCP1. SAP binds to the central core of the C4BP. In contrast, PS binds to CCP1 of the single β chain present in C4BPβ+. PS indicates protein S; LRP, low-density lipoprotein receptor-related protein; SAP, serum amyloid protein. This figure was prepared based on different sources, particularly Blom.⁷⁶