C4c C4b-binding protein Complement factor I C4b-binding protein:Factor I C4d Complement factor I inactivates C4BP-bound C4b Authored: Jupe, S, 2010-10-26 C4b-binding protein is a cofactor in Factor I mediated C4b proteolysis. C4b is cleaved, releasing C4c, leaving C4d bound to the cell surface. Edited: Jupe, S, 2010-11-01 Pubmed1386357 Reactome Database ID Release 43981637 Reactome, http://www.reactome.org ReactomeREACT_118719 Reviewed: Bradley, DT, 2012-02-13 Reviewed: Fraczek, LA, 2012-02-13 has a Stoichiometric coefficient of 7