Glycan shield and epitope masking of a coronavirus spike protein observed by cryo-electron microscopy
The article reports the 3.4-Å-resolution cryo-EM reconstruction of the Human coronavirus NL63 spike glycoprotein trimer, which mediates entry into host cells and is the main target of neutralizing antibodies during infection. The map resolves the extensive glycan shield obstructing the protein surface and, in combination with mass spectrometry, provides a structural framework to understand the accessibility to antibodies.
The structure reveals the complete architecture of the fusion machinery including the triggering loop and the C-terminal domains, which contribute to anchoring the trimer to the viral membrane. The data further suggest that Human coronavirus NL63 and other coronaviruses use molecular trickery, based on epitope masking with glycans and activating conformational changes, to evade the immune system of infected hosts.