The spread of SARS-CoV-2 variants in the population depends on their ability to anchor the ACE2 receptor in the host cells. Differences in the electrostatic potentials of the spike protein RBD (electropositive/basic) and ACE2 receptor (electronegative/acidic) play a key role in both the rapprochement and the recognition of the coronavirus by the cell receptors. Accordingly, point mutations that result in an increase in electropositively charged residues, e.g., arginine and lysine, especially in the RBD of spike proteins in the SARS-CoV-2 variants, could contribute to their spreading capacity by favoring their recognition by the electronegatively charged ACE2 receptors. All SARS-CoV-2 variants that have been recognized as being highly transmissible, such as the kappa (κ), delta (δ) and omicron (o) variants, which display an enhanced electropositive character in their RBDs associated with a higher number of lysine- or arginine-generating point mutations. Lysine and arginine residues also participate in the enhanced RBD-ACE2 binding affinity of the omicron variant, by creating additional salt bridges with aspartic and glutamic acid residues from ACE2. However, the effects of lysine- and arginine-generating point mutations on infectivity is more contrasted, since the overall binding affinity of omicron RBD for ACE2 apparently results from some epistasis among the whole set of point mutations.
Keywords: ACE2; COVID-19; SARS-CoV-2; coulombic charges; delta variant; mu variant; omicron variant; point mutation; spike protein; surface electrostatic potential; transmissibility.