C3
Function
C3 plays a central role in the activation of the complement system. Its processing by C3 convertase is the central reaction in both classical and alternative complement pathways. After activation C3b can bind covalently, via its reactive thioester, to cell surface carbohydrates or immune aggregates.
Derived from proteolytic degradation of complement C3, C3a anaphylatoxin is a mediator of local inflammatory process. It induces the contraction of smooth muscle, increases vascular permeability and causes histamine release from mast cells and basophilic leukocytes. In chronic inflammation, acts as a chemoattractant for neutrophils (By similarity).
C3-beta-c
Acts as a chemoattractant for neutrophils in chronic inflammation.
Post-translational modifications
C3b is rapidly split in two positions by factor I and a cofactor to form iC3b (inactivated C3b) and C3f which is released. Then iC3b is slowly cleaved (possibly by factor I) to form C3c (beta chain + alpha' chain fragment 1 + alpha' chain fragment 2), C3dg and C3f. Other proteases produce other fragments such as C3d or C3g (By similarity).
Phosphorylated by FAM20C in the extracellular medium.
Cellular localization
- Secreted
Alternative names
Complement C3, C3