The structures of secretory and dimeric immunoglobulin a

Sonya Kumar Bharathkar, Benjamin W. Parker, Andrey G. Malyutin, Nandan Haloi, Kathryn E. Huey-Tubman, Emad Tajkhorshid, Beth M. Stadtmueller

Research output: Contribution to journalArticlepeer-review


Secretory (S) Immunoglobulin (I) A is the predominant mucosal antibody, which binds pathogens and commensal microbes. SIgA is a polymeric antibody, typically containing two copies of IgA that assemble with one joining-chain (JC) to form dimeric (d) IgA that is bound by the polymeric Igreceptor ectodomain, called secretory component (SC). Here we report the cryo-electron microscopy structures of murine SIgA and dIgA. Structures reveal two IgAs conjoined through four heavy-chain tailpieces and the JC that together form a β-sandwich-like fold. The two IgAs are bent and tilted with respect to each other, forming distinct concave and convex surfaces. In SIgA, SC is bound to one face, asymmetrically contacting both IgAs and JC. The bent and tilted arrangement of complex components limits the possible positions of both sets of antigen binding fragments (Fabs) and preserves steric accessibility to receptor binding sites, likely influencing antigen binding and effector functions.

Original languageEnglish (US)
Article numbere56098
Pages (from-to)1-29
Number of pages29
StatePublished - Oct 2020

ASJC Scopus subject areas

  • General Neuroscience
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology


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