外域
分泌成分
抗体
弯曲分子几何
J链
受体
效应器
化学
免疫球蛋白A
分泌性IgA
抗原
细胞生物学
生物
免疫学
免疫球蛋白G
生物化学
有机化学
作者
Sonya Kumar Bharathkar,Benjamin W. Parker,Andrey G. Malyutin,Nandan Haloi,Kathryn E. Huey-Tubman,Emad Tajkhorshid,Beth M. Stadtmueller
标识
DOI:10.1101/2020.02.16.951780
摘要
Abstract 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.
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