May 4, 2020 / JV Chamary, Contributor
The race to develop vaccines and drugs against SARS-CoV-2 is centred on the spike proteins that the coronavirus uses to invade human cells. But like many proteins built from the materials a virus steals from its host, the spike isn’t simply a protein but a ‘glycoprotein’ covered in carbohydrate sugars.
Sugars or ‘glycans’ play many roles in nature, such as helping proteins fold into stable structures. “The sugars are really central in orchestrating that folding mechanism,” says Professor Max Crispin, a glycobiologist at the University of Southampton. And in the case of viruses like SARS-CoV-2, those sugars also form camouflage. “This spike is like the wolf in sheep’s clothing because the carbohydrates that cover it are human-derived.”
Crispin’s team recently mapped the sugars attached to SARS-CoV-2’s spike, as reported in a new study published in the journal Science. This research identified the location of 22 ‘glycosylation sites’ where glycans are attached to the spike (66 in total as the protein consists of three identical parts) and the types of sugar at each site. This work involved using mass spectrometry, chopping-up the protein and weighing the fragments in a vacuum to determine the chemical composition of each piece. The details of the glycans were then mapped onto the structure of the spike protein.