Complement C3 is major component in the both the classical and alternative complement activation pathways. C3 is cleaved into two chains (alpha and beta) by C3 convertases. This entry represents the second CUB domain [2]. This domain and the first CUB (Pfam:PF21406) flank the TE domain. The CUB, TE and MG8 domains form a massive, tightly packed super domain.

1: Structures of complement component C3 provide insights into the function and evolution of immunity. Janssen BJ, Huizinga EG, Raaijmakers HC, Roos A, Daha MR, Nilsson-Ekdahl K, Nilsson B, Gros P; Nature. 2005;437:505-511. PMID:16177781

2: The structure of bovine complement component 3 reveals the basis for thioester function. Fredslund F, Jenner L, Husted LB, Nyborg J, Andersen GR, Sottrup-Jensen L; J Mol Biol. 2006;361:115-127. PMID:16831446

3: Structure of C3b reveals conformational changes that underlie complement activity. Janssen BJ, Christodoulidou A, McCarthy A, Lambris JD, Gros P; Nature. 2006;444:213-216. PMID:17051160

4: Structure of C3b in complex with CRIg gives insights into regulation of complement activation. Wiesmann C, Katschke KJ, Yin J, Helmy KY, Steffek M, Fairbrother WJ, McCallum SA, Embuscado L, DeForge L, Hass PE, van Lookeren Campagne M; Nature. 2006;444:217-220. PMID:17051150

5: Structures of C3b in complex with factors B and D give insight into complement convertase formation. Forneris F, Ricklin D, Wu J, Tzekou A, Wallace RS, Lambris JD, Gros P; Science. 2010;330:1816-1820. PMID:21205667