Vulnerabilities in coronavirus glycan shields despite extensive glycosylation

Yasunori Watanabe; Zachary T. Berndsen; Jayna Raghwani; Gemma E. Seabright; Joel D. Allen; Jason S. McLellan; Ian A. Wilson; Thomas A. Bowden; Andrew B. Ward; Max Crispin

Man5GlcNAc2 to Man9GlcNAc2 glycans all present, without one particular dominant peak, as is the case for some viral glycoproteins, such as HIV-1 Env 36 In order to ascertain the precise structures of N-linked glycans from the released pool, the glycans of each coronavirus S protein were analysed by negative-ion ion-mobilityelectrospray ionisation mass spectrometry (IM-ESI MS) ( Supplementary Fig. 1 ). Consistent with the UPLC data, IM-ESI MS confirmed an array of complex-type glycans ranging from mono-to tetra-antennary, but also oligomannose-and hybrid-type glycans. The glycan compositions characterised in the spectra were largely invariant among the coronaviruses with no major structural differences observed. Oligomannose-type glycans (M5 to M9; Man5GlcNAc2-Man9GlcNAc2) (green) and complex-type glycans (magenta) were identified by Endo H digestion, with quantification of major glycan types summarised as a pie chart. Oligomannose-type glycans are schematically annotated with mannose residues as green circles and GlcNAc residues as blue squares.