This domain is found in the alpha and beta chains of Complement component C8 (C8A/B), in Complement components C6 (C6) from humans, constituents of the membrane attack complex (MAC) that play a key role in the innate and adaptive immune response by forming pores in the plasma membrane of target cells. This entry represents the rigid, disulfide-rich epidermal growth factor (EGF) domain, which is included in the regulatory segment of these proteins [1,2]. It is found C-terminal to the membrane attack complex perforin domain Pfam:PF01823 and N-terminal to the thrombospondin type 1 domain Pfam:PF00090.

1: Structure of human C8 protein provides mechanistic insight into membrane pore formation by complement. Lovelace LL, Cooper CL, Sodetz JM, Lebioda L; J Biol Chem. 2011;286:17585-17592. PMID:21454577

2: Structure of complement C6 suggests a mechanism for initiation and unidirectional, sequential assembly of membrane attack complex (MAC). Aleshin AE, Schraufstatter IU, Stec B, Bankston LA, Liddington RC, DiScipio RG; J Biol Chem. 2012;287:10210-10222. PMID:22267737