C4B
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 1HZF, 4FXG, 4FXK, 4XAM,%%s4XAM
Identifiers
Aliases	C4B, C4B1, C4B12, C4B2, C4B3, C4B5, C4BD, C4B_2, C4F, CH, CO4, CPAMD3, Complement component 4B, complement component 4B (Chido blood group), complement C4B (Chido blood group)
External IDs	OMIM: 120820 MGI: 88228 HomoloGene: 36030 GeneCards: C4B
Gene location (Human) Chr. Chromosome 6 (human)[1] Band 6p21.33 Start 32,014,795 bp[1] End 32,035,418 bp[1]
Gene location (Mouse) Chr. Chromosome 17 (mouse)[2] Band 17 B1|17 18.29 cM Start 34,947,354 bp[2] End 34,962,856 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in right lobe of liver right lobe of thyroid gland left lobe of thyroid gland tibial nerve anterior pituitary spleen left uterine tube kidney substantia nigra right coronary artery Top expressed in zone of skin adrenal gland white adipose tissue synovial joint ankle joint spleen liver uterus esophagus urinary bladder More reference expression data BioGPS n/a
Gene ontology Molecular function endopeptidase inhibitor activity complement component C1q complex binding serine-type endopeptidase activity complement binding carbohydrate binding Cellular component extracellular region plasma membrane extracellular exosome blood microparticle cell projection dendrite cell junction synapse axon neuronal cell body extracellular space endoplasmic reticulum lumen Biological process complement activation inflammatory response positive regulation of apoptotic cell clearance regulation of complement activation negative regulation of endopeptidase activity complement activation, classical pathway immune system process innate immune response proteolysis post-translational protein modification opsonization Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 721 12268 Ensembl ENSG00000228267 ENSG00000236625 ENSG00000224389 ENSG00000228454 ENSG00000224639 n/a ENSMUSG00000073418 UniProt P0C0L4 P0C0L5 P01029 RefSeq (mRNA) NM_001002029 NM_009780 RefSeq (protein) NP_001239133 NP_009224 NP_001229752 NP_033910 Location (UCSC) Chr 6: 32.01 – 32.04 Mb Chr 17: 34.95 – 34.96 Mb PubMed search [3] [4]
Wikidata
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Complement component 4B (Chido blood group) is a kind of the Complement component 4 protein that in humans is encoded by the C4B gene.^[5]

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 RCCX locus within the major histocompatibility complex (MHC) class III region on chromosome 6.^[6][7] 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].^[5] Each copy of the gene, due to five adjacent nucleotide substitutions cause four amino acid changes and immunological subfunctionalization,^[8] can be of one of two types: C4A and C4B.^[9] 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.^[7]