A J chain is a protein part of the antibodies IgM and IgA.[4] It’s a 137 residue polypeptide,[5] encoded by the IGJ gene.[6][7][8]
Contents
Construction[edit]
The J Chain’s molecular weight is roughly 15 kDa. It displays a typical immunoglobulin folding construction of two β-pleated sheets of 4 ribbons folded in opposition to each other. It has 8 cystine residues. Two of those residues hyperlink the α chains of IgA or the μ chains of IgM by way of disulfide bridges, successfully serving because the “glue” between two Fc areas of the antibody.[9]
The J-chain exhibits a big diploma of homology between avian and human species, suggesting that it serves an vital operate.[9]
Perform[edit]
The J Chain is required for IgM or IgA to be secreted into mucosa.[5] As a part of a polymeric immunoglobulin (pIg), the J-chain is crucial for binding of pIg to the pIgR, which kinds the secretory part upon excretion of the secretory pIg by epithelial cells.[10] This binding facilitates transport of the J-chain optimistic pIg molecules from the basal to the apical sides of epithelial cells.
As a result of IgM and IgA are the one two kinds of antibody that polymerize, preliminary hypotheses acknowledged that J chain was required for polymerization. Nonetheless, it was subsequently discovered that IgM is ready to polymerize within the absence of J chain as each a pentamer and a hexamer, nevertheless, each of those exist to lesser numbers in organisms missing J chains. In such circumstances, there are additionally fewer IgA dimers.[5]
The J-chain additionally performs a job within the activation of complement. J-chain destructive IgM hexamers are 15-20 instances more practical at activating complement than J-chain optimistic IgM pentamers.[10] A consequence of this lack of complement activation is it permits J-chain optimistic pIgM to bind antigens with out inflicting extreme injury to epithelial membranes by means of complement activation.
References[edit]
Additional studying[edit] – “j protein immunoglobulins”
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“j protein immunoglobulins”