Fig. 3: Structural and biophysical effects of Kappa and Delta S protein mutations on ACE2 binding.

a The global and focus-refined cryo-EM structures for the Kappa and Delta variant S proteins in complex with ACE2. A more focused view to show the quality of the cryo-EM density at the S protein – ACE2 interface is provided in Supplementary Fig. 6. b Electrostatic surface potentials for the wild-type, Kappa and Delta S protein–ACE2 complexes. Electrostatic potential colouring spans −10 kcal mol⁻¹ e⁻¹ (darkest red) to 10 kcal mol⁻¹ e⁻¹ (darkest blue). We previously reported the structure of the wild-type S protein–ACE2 complex and we use this model here to generate the wild-type electrostatic surface²³. c Biolayer interferometry (BLI) sensorgrams for the wild-type, Kappa, and Delta variant S protein–ACE2 binding interaction. The S protein concentrations utilised are: 1000 nM (blue), 500 nM (red), 250 nM (green), 125 nM (magenta). The k_on and k_off rate constants are presented in Supplementary Fig. 3. Source data are provided as a Source Data file.