The high infectivity of the SARS-CoV-2 Omicron variant is associated with an exclusive S477N spike receptor-binding domain mutation

Abstract

The spike glycoprotein receptor-binding domain (RBD) of SARS-CoV-2 facilitates viral binding to the ACE2 receptor and mediates viral infectivity. The Delta and Omicron variants of concern are the most infectious strains, presenting mutated amino acid residues in their spike RBD. The Omicron variant quickly dominated the COVID-19 pandemic, indicating its greater spreadability. Omicrons spreading might be associated with mutational substitutions at spike RBD residues. We employed in silico molecular dynamics (MD) simulation of the spike RBD-ACE2 interaction to compare the impact of specific mutations of the Delta and Omicron variants. The MD of the spike-ACE2 interaction showed the following: i) the amino acid profile involved in the spike-ACE2 interaction differs between Delta and Omicron; ii) the Omicron variant establishes several additional interactions, highlighting the spike RBD (S477), which is a flexible mutational residue. Since the S477N mutation is exclusive to Omicron, which may initiate binding with ACE2, the increased infectivity of Omicron might be associated not only with a mutated RBD but also with unmutated (e.g., G476 and L492) residues, initiating binding due to the influence of the N477 mutation. Compared to previous variants, Omicrons N477 residue represents a novelty within the spike-ACE2 interaction dynamics interface.