A single de novo substitution in SARS-CoV-2 spike informs enhanced adherence to human ACE2.

SARS-CoV-2 initiates colonization of host cells by binding to cell membrane ACE2 receptor. This binding is mediated by the viral spike receptor binding domain (RBD). The COVID-19 pandemic has brought devastating consequences at a clinical, social and economical levels. Therefore, anticipation of potential novel SARS-causing species or SARS-CoV-2 variants with enhanced binding to ACE2 is key in the prevention of future threats to come. We have characterized a de novo single substitution, Q498Y, in SARS-CoV-2 RBD that confers stronger adherence to ACE2. While the SARS-CoV-2 {beta} variant, which includes three simultaneous amino acid replacements, induces a 4-fold stronger affinity, a single Q498Y substitution results in 2.5-fold tighter binding, compared to the Wuhan-Hu-1 SARS-CoV-2 2019 strain. Additionally, we crystallized RBDQ498Y complexed with ACE2 and provide here the structural basis for this enhanced affinity. These studies inform a rationale for prevention of potential SARS-causing viruses to come.