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Tidey, Keith

University of British Columbia

SARS-CoV-2 is the infectious virus that rapidly spread to give rise to the COVID-19 pandemic. The objectives of this thesis project were to examine the XBB.1.5 variant of SARS-CoV-2 with respect to its newly acquired F486P mutation contained within the spike glycoprotein, as it was suspected to play a critical role in its enhanced binding to ACE2 relative to its predecessor, XBB.1. To achieve this, the F486P mutation was introduced into four previously identified spike protein variants, while the mutation was reverted to a phenylalanine in XBB.1.5 and the resulting mutant proteins were examined through cryo-EM and binding assays. Global reconstructions revealed no major structural rearrangements in the core spike, which was resolved to a resolution of ~2.5Å in the best ordered regions. A focused refinement of the RBD bound to hACE2 allowed for unambiguous placement of the P486F mutation within the modified XBB.1.5 RBD, verifying a conserved binding motif to ACE2 despite the introduced mutation; in effect, this residue was observed to restore the structure of the binding loop to what was observed in previous spikes and reposition the adjacent asparagine to modulate binding, confirming that this proline is sufficient to reshape the local region by itself and is not reliant on the remaining XBB.1.5 structure. In summary, the studies presented here provide additional insights that contribute to our understanding of the key residues in the SARS-CoV-2 spike glycoprotein that modulate binding of the virus to the cell surface. Studies like these remain crucial as the virus continues to evolve, posing an ongoing global health threat.

Text

2025-02-27

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/90437

Biochemistry and Molecular Biology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/