RT Journal Article
SR Electronic
T1 The Structures of Secretory and Dimeric Immunoglobulin A
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.02.16.951780
DO 10.1101/2020.02.16.951780
A1 Sonya Kumar Bharathkar
A1 Benjamin W. Parker
A1 Andrey G. Malyutin
A1 Nandan Haloi
A1 Kathryn E. Huey-Tubman
A1 Emad Tajkhorshid
A1 Beth M. Stadtmueller
YR 2020
UL http://biorxiv.org/content/early/2020/10/15/2020.02.16.951780.abstract
AB 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 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.Competing Interest StatementThe authors have declared no competing interest.