北京大学肖俊宇课题组解析免疫球蛋白M（IgM）结构。2020年2月6日，《科学》在线发表了这一成果。

他们报告了与连接链（J链）和聚合免疫球蛋白受体（pIgR）胞外域复合的人IgM Fc区的冷冻电镜结构。IgM-Fc五聚体形成不对称结构，类似于带有缺失三角形的六边形。IgM-Fc的尾翼包装成淀粉样结构以稳定五聚体。J链封住尾翼组件，并桥接IgM-Fc与pIgR之间的相互作用，该相互作用经历了较大的构象变化，从而与IgM–J复合物接合。这些结果为IgM的功能提供了结构基础。

据了解，IgM在体液和粘膜免疫中都起着关键作用。它的组装和运输取决于J链和pIgR，但这些过程的潜在分子机制尚不清楚。

附：英文原文

Title: Structural insights into immunoglobulin M

Author: Yaxin Li, Guopeng Wang, Ningning Li, Yuxin Wang, Qinyu Zhu, Huarui Chu, Wenjun Wu, Ying Tan, Feng Yu, Xiao-Dong Su, Ning Gao, Junyu Xiao

Issue&Volume: 2020/02/06

Abstract: AbstractImmunoglobulin M (IgM) plays a pivotal role in both humoral and mucosal immunity. Its assembly and transport depend on the joining chain (J-chain) and the polymeric immunoglobulin receptor (pIgR), but the underlying molecular mechanisms of these processes are unclear. Here we report a cryo-electron microscopy structure of the Fc region of human IgM in complex with the J-chain and pIgR ectodomain. The IgM-Fc pentamer is formed asymmetrically, resembling a hexagon with a missing triangle. The tailpieces of IgM-Fc pack into an amyloid-like structure to stabilize the pentamer. The J-chain caps the tailpiece assembly and bridges the interaction between IgM-Fc and pIgR, which undergoes a large conformational change to engage the IgM–J complex. These results provide a structural basis for the function of IgM.

DOI: 10.1126/science.aaz5425

Source: https://science.sciencemag.org/content/early/2020/02/05/science.aaz5425