| UniProt Protein Function: | Non-enzymatic component of 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. |
| NCBI Summary: | This gene encodes the basic form of complement factor 4, part of the classical activation pathway. The protein is expressed as a single chain precursor which is proteolytically cleaved into a trimer of alpha, beta, and gamma chains prior to secretion. The trimer provides a surface for interaction between the antigen-antibody complex and other complement components. The alpha chain may be cleaved to release C4 anaphylatoxin, a mediator of local inflammation. Deficiency of this protein is associated with systemic lupus erythematosus. This gene localizes to the major histocompatibility complex (MHC) class III region on chromosome 6. Varying haplotypes of this gene cluster exist, such that individuals may have 1, 2, or 3 copies of this gene. In addition, this gene exists as a long form and a short form due to the presence or absence of a 6.4 kb endogenous HERV-K retrovirus in intron 9. [provided by RefSeq, Jul 2008] |
| UniProt Code: | P0C0L5 |
| NCBI GenInfo Identifier: | 178557739 |
| NCBI Gene ID: | 721 |
| NCBI Accession: | NP_001002029.3 |
| UniProt Secondary Accession: | P0C0L5,P01028, P78445, Q13160, Q13906, A6H8M8, A6NHJ5 A7E2V2, B0QZR6, B0V2C8, B2RUT6, B7ZVZ6, |
| UniProt Related Accession: | P0C0L5 |
| Molecular Weight: | 187,704 Da |
| NCBI Full Name: | complement C4-B preproprotein |
| NCBI Synonym Full Names: | complement C4B (Chido blood group) |
| NCBI Official Symbol: | C4B |
| NCBI Official Synonym Symbols: | CH; C4F; CO4; C4B1; C4B2; C4B3; C4B5; C4BD; C4B12; C4B_2; CPAMD3 |
| NCBI Protein Information: | complement C4-B |
| UniProt Protein Name: | Complement C4-A |
| UniProt Synonym Protein Names: | Acidic complement C4; C3 and PZP-like alpha-2-macroglobulin domain-containing protein 2 |
| Protein Family: | Complement C4 |
| UniProt Gene Name: | C4A |
