J chain

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Immunoglobulin J polypeptide, linker protein for immunoglobulin alpha and mu polypeptides
Identifiers
Symbols IGJ ; IGCJ; JCH
External IDs OMIM147790 MGI96493 HomoloGene16958 GeneCards: IGJ Gene
RNA expression pattern
PBB GE IGJ 212592 at tn.png
More reference expression data
Orthologs
Species Human Mouse
Entrez 3512 16069
Ensembl ENSG00000132465 ENSMUSG00000067149
UniProt P01591 P01592
RefSeq (mRNA) NM_144646 NM_152839
RefSeq (protein) NP_653247 NP_690052
Location (UCSC) Chr 4:
71.52 – 71.55 Mb
Chr 5:
88.52 – 88.53 Mb
PubMed search [1] [2]
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.
The dimeric IgA molecule.
1: Heavy chains.
2: Light chains.
3: J-chain.
4: Secretory component.

A J chain is a protein component of the antibodies IgM and IgA.[1] It is a 137 residue polypeptide,[2] encoded by the IGJ gene.[3][4][5]

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.[6]

The J-chain shows a large degree of homology between avian and human species, suggesting that it serves an important function.[6]

Function[edit]

The J Chain is required for IgM or IgA to be secreted into mucosa.[2]

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 case, there are also fewer IgA dimers.[2]

References[edit]

  1. ^ Levinson. Medical Microbiology and Immunology (11 ed.). McGrawHill. pp. 405–6. 
  2. ^ 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. 
  3. ^ 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 386334. PMID 3016707. 
  4. ^ 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 2189063. PMID 2984306. 
  5. ^ "Entrez Gene: IGJ immunoglobulin J polypeptide, linker protein for immunoglobulin alpha and mu polypeptides". 
  6. ^ 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]