Fig. 3: Binding of ACE2 receptor to bat virus and SARS-CoV-2 S proteins.

a, Plot of surface biolayer amplitude measurement as a function of ACE2 concentration with the data for S from SARS-CoV-2 (blue, K_d calculated as 91 ± 18 nM) and from the bat virus (red, K_d estimated to be >40 μM). K_d for the SARS-CoV-2 protein was calculated from kinetic constants (k_off = 0.0105 s⁻¹ and k_on = 1.56 × 10⁵ m⁻¹ s⁻¹) and was 67.5 ± 9 nM. b,c, Ribbon representation of modeled molecular interactions between ACE2 (green) with RBD from S in SARS-CoV-2 (blue) (both PDB 6VW1)²¹ and bat virus (red, this study). b, Details of a hydrophobic pocket on ACE2 that accommodates a phenylalanine residue from the SARS-CoV-2 S RBD. c, Two salt bridges and a charged hydrogen bond linking SARS-CoV-2 S RBD to ACE2, while the interface with bat virus S RBD is not able to make these interactions and presents a potential steric clash between Tyr493 and ACE2 Lys31.