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Structural insights into immunoglobulin M


Dr. Junyu Xiao published a paper in Science.

Immunoglobulin 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.

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