Aliases for C4B_2 Gene
Previous GeneCards Identifiers for C4B_2 Gene
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. This GeneID and its associated RefSeq record represent a second copy of C4B found on ALT_REF_LOCI_7. [provided by RefSeq, Jul 2011]
GeneCards Summary for C4B_2 Gene
C4B_2 (Complement Component 4B (Chido Blood Group), Copy 2) is a Protein Coding gene. Diseases associated with C4B_2 include Lupus Erythematosus and Systemic Lupus Erythematosus. Among its related pathways are Creation of C4 and C2 activators and Immune System.
UniProtKB/Swiss-Prot for C4B_2 Gene
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.