J chain

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JCHAIN
Identifiers
Aliases JCHAIN, IGCJ, JCH, IGJ, J chain, joining chain of multimeric IgA and IgM
External IDs MGI: 96493 HomoloGene: 16958 GeneCards: JCHAIN
RNA expression pattern
PBB GE IGJ 212592 at fs.png
More reference expression data
Orthologs
Species Human Mouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_144646

NM_152839

RefSeq (protein)

NP_653247

NP_690052.2
NP_690052

Location (UCSC) Chr 4: 70.66 – 70.68 Mb Chr 5: 88.52 – 88.53 Mb
PubMed search [1] [2]
Wikidata
View/Edit Human View/Edit Mouse
Immunoglobulin M (IgM) pentameric antibody molecule (consisting of five base units).
1: Base unit.
2: Heavy chains.
3: Light chains.
4: J chain.
5: Intermolecular disulfide bonds.
Schematic of immunoglobulin A dimer showing H-chain (blue), L-chain (red), J-chain (magenta) and secretory component (yellow).

A J chain is a protein component of the antibodies IgM and IgA.[3] It is a 137 residue polypeptide,[4] encoded by the IGJ gene.[5][6][7]

Structure[edit]

The J Chain's molecular weight is approximately 15 kDa. It exhibits a standard immunoglobulin folding structure of two β-pleated sheets of four ribbons folded against one another. It has 8 cystine residues. Two of these residues link the α chains of IgA or the μ chains of IgM via disulfide bridges, effectively serving as the "glue" between two Fc regions of the antibody.[8]

The J-chain shows a large degree of homology between avian and human species, suggesting that it serves an important function.[8]

Function[edit]

The J Chain is required for IgM or IgA to be secreted into mucosa.[4]

Because IgM and IgA are the only two types of antibody that polymerize, initial hypotheses stated that J chain was required for polymerization. However, it was subsequently found that IgM is able to polymerize in the absence of J chain as both a pentamer and a hexamer, however, both of these exist to lesser numbers in organisms lacking J chains. In such cases, there are also fewer IgA dimers.[4]

References[edit]

  1. ^ "Human PubMed Reference:". 
  2. ^ "Mouse PubMed Reference:". 
  3. ^ Levinson. Medical Microbiology and Immunology (11 ed.). McGrawHill. pp. 405–6. 
  4. ^ a b c Schroeder, Harry; Wald, David; Greenspan, Neil (2008). "Chapter 4: Immunoglobulins: Structure and Function". In Paul, William. Fundamental Immunology (Book) (6th ed.). Philadelphia, PA: Lippincott Williams & Wilkins. pp. 125–151. ISBN 0-7817-6519-6. 
  5. ^ Max EE, McBride OW, Morton CC, Robinson MA (Sep 1986). "Human J chain gene: chromosomal localization and associated restriction fragment length polymorphisms". Proc Natl Acad Sci U S A. 83 (15): 5592–6. doi:10.1073/pnas.83.15.5592. PMC 386334Freely accessible. PMID 3016707. 
  6. ^ Max EE, Korsmeyer SJ (May 1985). "Human J chain gene. Structure and expression in B lymphoid cells". J Exp Med. 161 (4): 832–49. doi:10.1084/jem.161.4.832. PMC 2189063Freely accessible. PMID 2984306. 
  7. ^ "Entrez Gene: IGJ immunoglobulin J polypeptide, linker protein for immunoglobulin alpha and mu polypeptides". 
  8. ^ a b Kiyono, Hiroshi; Kunisawa, Jaw; McGhee, Jerry; Mestecky, Jiri (2008). "Chapter 31: The Mucosal Immune System". In Paul, William. Fundamental Immunology (Book) (6th ed.). Philadelphia, PA: Lippincott Williams & Wilkins. pp. 983–1030. ISBN 0-7817-6519-6. 

Further reading[edit]