Cleavage of C4 exposes an active thioester bond on the large fragment C4b that allows it to bind covalently to hydroxyl or amino groups on target surfaces. This binding is regulated by the hydrolysis reaction that irreversibly inactivates C4b [Law SK and Dodds AW 1997; Dodds AW et al 1996]. Surface-bound C4b forms the basis for the formation of C3/C5 convertases.
This event was inferred from the curated human reaction.
Juul-Madsen, HR, Norup, LR
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