Complement Component 4b (C4b)

CPAMD3; C4F; CO4; C4B1; C4B3; CH; C4(Chido Blood Group); Basic complement C4; C4a anaphylatoxin; C3 and PZP-like alpha-2-macroglobulin domain-containing protein 3

SPN	V527
HGNC	1324
MGI	88228
PubMed	23259761
RGD	620005
UniProt	P0C0L5
Wiki	C4B

Complement component 4 is a protein involved in the complement system.It is cleaved into proteins 4a and 4b.  C4b forms part of C3-convertase, in conjunction with 2a: C4b can bind CR1. C4b is the large fragment formed when Complement C4 is cleaved by Complement C1S. The membrane-bound C4b binds Complement C2A, a SERINE PROTEASE, to form C4b2a (CLASSICAL PATHWAY C3 CONVERTASE) and subsequent C4b2a3b (CLASSICAL PATHWAY C5 CONVERTASE).

INon-enzymatic component of the C3 and C5 convertases and thus essential for the propagation of the classical complement pathway. Covalently binds to immunoglobulins and immune complexes and enhances the solubilization of immune aggregates and the clearance of IC through CR1 on erythrocytes. C4A isotype is responsible for effective binding to form amide bonds with immune aggregates or protein antigens, while C4B isotype catalyzes the transacylation of the thioester carbonyl group to form ester bonds with carbohydrate antigens.

Derived from proteolytic degradation of complement C4, C4a 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.

Reference

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