| Post Translational Modifications | Prior to secretion, the single-chain precursor is enzymatically cleaved to yield non-identical chains alpha, beta and gamma. During activation, the alpha chain is cleaved by C1 into C4a and C4b, and C4b stays linked to the beta and gamma chains. Further degradation of C4b by C1 into the inactive fragments C4c and C4d blocks the generation of C3 convertase. The proteolytic cleavages often are incomplete so that many structural forms can be found in plasma. |
| Function | Non-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. |
| Protein Name | Complement C4-BBasic Complement C4C3 And Pzp-Like Alpha-2-Macroglobulin Domain-Containing Protein 3 Cleaved Into - Complement C4 Beta Chain - Complement C4-B Alpha Chain - C4a Anaphylatoxin - C4b-B - C4d-B - Complement C4 Gamma Chain |
| Database Links | Reactome: R-HSA-166663Reactome: R-HSA-174577Reactome: R-HSA-977606 |
| Cellular Localisation | SecretedSynapseCell ProjectionAxonDendrite |
| Alternative Protein Names | Complement C4-B proteinBasic Complement C4 proteinC3 And Pzp-Like Alpha-2-Macroglobulin Domain-Containing Protein 3 Cleaved Into - Complement C4 Beta Chain - Complement C4-B Alpha Chain - C4a Anaphylatoxin - C4b-B - C4d-B - Complement C4 Gamma Chain proteinC4B proteinCO4 proteinCPAMD3.C4B_2 protein |
Information sourced from Uniprot.org
