J chain
protein-coding gene in the species Homo sapiens
The Joining (J) chain is a protein component that links monomers of antibodies IgM and IgA to form polymeric antibodies capable of secretion. The J chain is well conserved in the jawed vertebrates, but its specific functions are yet to be fully understood. It is a 137 residue polypeptide, encoded by the IGJ gene.
Structure
The J chain is a glycoprotein. The preprotein has a 22-residue signal peptide that proceeds the actually secreted J chain (137 residues). The unglycosylated molecular weight of the secreted J chain is 15 kDa. The glycosylated molecular weight is 16.42 kDa (7.5% carbohydrate by weight).
The J chain's primary structure is unusually acidic having a high content of negatively charged amino acids. It has eight cysteine residues, six of which are involved in intramolecular disulfide bonds while the remaining two function to bind the Fc tailpiece regions of IgA or IgM antibodies, the α chain and μ chain respectively. An N-linked carbohydrate resulting from N-glycosylation is also essential in the protein's incorporation to antibody polymers.
The public source identifies “J chain” as protein-coding gene in the species Homo sapiens. This brief keeps that definition visible, then builds a research path around chain, protein-coding and gene.
Why this record matters
A short description can identify a subject without explaining its stakes. For “J chain”, the useful work is to connect “protein-coding gene in the species Homo sapiens” to the records capable of establishing context and consequence.
Stable identifiers, scientific names and standards terminology offer the best bridge between this overview and specialist evidence. The source revision retrieved here is dated Aug 9, 2026. The linked authority identifier is Q18027731. None of the 0 selected statements returned an explicit reference.
A general summary may omit uncertainty, sample limits or methodological disagreement that is explicit in the technical record. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Check terminology, classification and the date of the cited evidence. Scientific names and technical consensus can change while older records retain historical value.
- Current terminology
- Classification context
- Finding cited technical literature
Primary datasets, specimen catalogues, standards bodies and the most recent peer-reviewed literature.
Three-step research path
- Establish the record: confirm the title “J chain”, its source revision and the description used here.
- Expand the search: follow J chain primary sources, J chain archive and chain research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “J chain”?
- Has classification or technical consensus changed since the cited source?
- Which observation, specimen, dataset or publication supports the account?
Search terms from this dossier
This entry incorporates text from “J chain” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.