The 3.1-Angstrom Cryo-electron Microscopy Structure of the Porcine Epidemic Diarrhea Virus Spike Protein in the Prefusion Conformation

Coronavirus spike proteins are large, densely glycosylated macromolecular machines that mediate receptor binding and membrane fusion to facilitate entry into host cells. This report describes the atomic-resolution structure of the spike protein from porcine epidemic diarrhea virus, a pathogenic alphacoronavirus that causes severe agricultural damage. The structure reveals a novel position for the sialic acid-binding attachment domain in the intact spike. We also observed shed fusion-suppressive capping subunits that displayed the putative receptor-binding domain in an accessible conformation. These observations provide a basis for understanding the molecular mechanisms that drive the earliest stages of alphacoronavirus infection and will inform future efforts to rationally design vaccines.