7JG2

Secretory Immunoglobin A (SIgA)

Summary for 7JG2

• Entry DOI: 10.2210/pdb7jg2/pdb
• Related: 7JG1
• EMDB information: 22309 22310
• Descriptor: Igh protein, Polymeric immunoglobulin receptor, Immunoglobulin J chain, ... (7 entities in total)
• Functional Keywords: immune system
• Biological source: Mus musculus (Mouse); More
• Total number of polymer chains: 6
• Total formula weight: 232033.27

Authors

Kumar Bharathkar, S.,Parker, B.P.,Malyutin, A.G.,Stadtmueller, B.M. (deposition date: 2020-07-18, release date: 2020-11-11, Last modification date: 2024-10-30)

Primary citation

Kumar Bharathkar, S.,Parker, B.W.,Malyutin, A.G.,Haloi, N.,Huey-Tubman, K.E.,Tajkhorshid, E.,Stadtmueller, B.
The structures of Secretory and dimeric Immunoglobulin A.
Elife, 9:-, 2020

PubMed Abstract: Secretory (S) Immunoglobulin (Ig) 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 Ig-receptor 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.

PubMed: 33107820
DOI: 10.7554/eLife.56098

Experimental method

ELECTRON MICROSCOPY (3.3 Å)