Complement factor I iC3b Complement factor I:Cell surface:FH,FHR3:C3b FH, FHR-3 Factor I inactivates Factor H-boundC3b Authored: Jupe, S, 2010-10-26 EC Number: 3.4.21 Edited: Jupe, S, 2010-11-01 Following the displacement of Bb from C3bBb, Factor I cleaves Factor H-bound C3b producing iC3b, which remains bound to the membrane. The majority of the C3b alpha chain is retained as two fragments which are tethered to the beta chain by disulphide bonds. iC3b is proteolytically inactive and cannot contribute to the complement cascade process, though it still contributes to opsonization. Pubmed3848661 Pubmed6219696 Reactome Database ID Release 43977371 Reactome, http://www.reactome.org ReactomeREACT_118841 Reviewed: Bradley, DT, 2012-02-13 Reviewed: Fraczek, LA, 2012-02-13