C4A | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Identifiers | |||||||||||||||||||||||||||||||||||||||||||||||||||
Aliases | C4A , C4, C4A2, C4A3, C4A4, C4A6, C4AD, C4S, CO4, CPAMD2, RG, complement component 4A (Rodgers blood group), complement C4A (Rodgers blood group) | ||||||||||||||||||||||||||||||||||||||||||||||||||
External IDs | OMIM: 120810; MGI: 88228; HomoloGene: 36030; GeneCards: C4A; OMA:C4A - orthologs | ||||||||||||||||||||||||||||||||||||||||||||||||||
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Wikidata | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Complement C4-A is a kind of the Complement component 4 protein that in humans is encoded by the C4A gene. [5]
This gene encodes the acidic 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 and type I diabetes mellitus. [6] [7] [8] [9] [10] [11] Excess production due to a copy number that is higher than normal has shown a high probability of a causal relationship with schizophrenia and bipolar disorder with psychosis, which could explain the hereditary nature of these illnesses. [12] This gene localizes to the RCCX locus within the major histocompatibility complex (MHC) class III region on chromosome 6. [13] [14] Varying haplotypes of this gene cluster exist, such that individuals may have 1, 2, or 3 copies of this gene. [5] Each copy of the gene, due to five adjacent nucleotide substitutions cause four amino acid changes and immunological subfunctionalization, [15] can be of one of two types: C4A and C4B . [16] Each gene contains 41 exons and has a dichotomous size variation between approximately 22 kb and 16 kb, with the longer variant being the result of the integration of the endogenous retrovirus HERV-K(C4) into intron 9. [14]