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Protein C4A PDB 1hzf.png
Available structures
PDBOrtholog search: PDBe RCSB
AliasesC4A, C4, C4A2, C4A3, C4A4, C4A6, C4AD, C4S, CO4, CPAMD2, RG, complement component 4A (Rodgers blood group), complement C4A (Rodgers blood group)
External IDsMGI: 88228 HomoloGene: 36030 GeneCards: C4A
Gene location (Human)
Chromosome 6 (human)
Chr.Chromosome 6 (human)[1]
Chromosome 6 (human)
Genomic location for C4A
Genomic location for C4A
Band6p21.33Start31,982,024 bp[1]
End32,002,681 bp[1]
RNA expression pattern
PBB GE C4A 214428 x at fs.png

PBB GE C4A 208451 s at fs.png
More reference expression data
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 6: 31.98 – 32 MbChr 17: 34.73 – 34.74 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

Complement C4-A is a 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] 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.[5]

See also[edit]


  1. ^ a b c ENSG00000206340, ENSG00000244731, ENSG00000227746 GRCh38: Ensembl release 89: ENSG00000244207, ENSG00000206340, ENSG00000244731, ENSG00000227746 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000073418 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:".
  4. ^ "Mouse PubMed Reference:".
  5. ^ a b "Entrez Gene: C4A complement component 4A (Rodgers blood group)".
  6. ^ Dawkins RL, Uko G, Christiansen FT, Kay PH (Sep 1983). "Low C4 concentrations in insulin dependent diabetes mellitus". British Medical Journal. 287 (6395): 839. doi:10.1136/bmj.287.6395.839-b. PMC 1549128. PMID 6412852.
  7. ^ Vergani D, Johnston C, B-Abdullah N, Barnett AH (Mar 1983). "Low serum C4 concentrations: an inherited predisposition to insulin dependent diabetes?". British Medical Journal. 286 (6369): 926–8. doi:10.1136/bmj.286.6369.926. PMC 1547358. PMID 6403137.
  8. ^ Mijovic CH, Fletcher JA, Bradwell AR, Barnett AH (Oct 1987). "Low C4 levels in type 1 (insulin-dependent) diabetes". Diabetologia. 30 (10): 824. doi:10.1007/bf00275752. PMID 3428499.
  9. ^ Thomsen M, Mølvig J, Zerbib A, de Preval C, Abbal M, Dugoujon JM, Ohayon E, Svejgaard A, Cambon-Thomsen A, Nerup J (1988). "The susceptibility to insulin-dependent diabetes mellitus is associated with C4 allotypes independently of the association with HLA-DQ alleles in HLA-DR3,4 heterozygotes". Immunogenetics. 28 (5): 320–7. doi:10.1007/BF00364230. PMID 3139557.
  10. ^ Jenhani F, Bardi R, Gorgi Y, Ayed K, Jeddi M (Apr 1992). "C4 polymorphism in multiplex families with insulin dependent diabetes in the Tunisian population: standard C4 typing methods and RFLP analysis". Journal of Autoimmunity. 5 (2): 149–60. doi:10.1016/0896-8411(92)90196-w. PMID 1352685.
  11. ^ Lhotta K, Auinger M, Kronenberg F, Irsigler K, König P (1996). "Polymorphism of complement C4 and susceptibility to IDDM and microvascular complications". Diabetes Care. 19 (1): 53&ndash, 55. doi:10.2337/diacare.19.1.53.

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Further reading[edit]