Fig. 2: Structural analysis of 3N39 mutant in complex with RBD.

a Overall structure. 3N39 ACE2 and RBD are shown in orange and green, respectively. The mutated residues in 3N39 are shown as cyan stick models. The expanded views of the PD1 region are provided in the inset. b Structural comparison of the K31N/E35K mutation site in 3N39 (left panel) with its corresponding site in WT (right panel). Hydrogen-bonding interactions (within 3.0 Å) are indicated by dashed lines. c Structural comparison of the L79F/A25V mutation site in 3N39 (left panel) with its corresponding site in WT (right panel). F486 residue of RBD and hydrophobic residues composing the F486 binding pocket of ACE2 are shown as stick models with transparent sphere models. d Comparison of the distances between Cβ atoms of S128 and V343 residues in the closed and open conformations. e Stabilizing effect of S138C/V343C mutation. Various versions of ACE2-His proteins, with (solid lines) or without (dotted lines) the S138C/V343C disulfide mutation (SS), were subjected to the differential scanning fluorimetry using SYPRO™ Orange as the probe dye. The Tm value for each mutant is estimated by the peak temperature of the -dF/dT plot, and the Tm shift caused by the SS mutation is shown at the bottom. The experiments were independently performed three times and similar results were obtained. One representative data were shown.