Fig. 2. Crystal structure of S protein RBD in complex with both Fabs AZD8895 and AZD1061.

a. Cartoon representation of crystal structure of S protein RBD in complex with AZD8895 and AZD1061 Fabs. RBD is shown in green, AZD8895 heavy chain in cyan, AZD8895 light chain in magenta, AZD1061 heavy chain in yellow, and AZD1061 light chain in pink. CDRs of AZD1061 are labeled.

b. Structure of RBD/AZD1061 complex is superimposed onto the structure of the RBD/ACE2 complex (PDB ID: 6M0J), using the RBD structure as the reference. The color scheme of the RBD/AZD1061 complex is the same as that in Fig. 2a. The RBD in the RBD/ACE2 complex is colored in blue, the human ACE2 peptidase domain in grey.

c. Structure of RBD/AZD1061 complex is superimposed onto the structure of spike with all RBD in “down” conformation (PDB ID: 6ZOY), using the RBD in one protomer as the reference. The color scheme of RBD/AZD1061 complex is the same as that in Fig. 2a. The three protomers of spike are colored in grey, blue, or purple respectively.

d. Structure of the RBD/AZD8895/AZD1061 complex is superimposed onto the structure of spike with one RBD in “up” conformation (PDB ID: 7CAK), using the RBD in “up” conformation as the reference. The color scheme of RBD/AZD1061 complex is the same as that in Fig. 2a. The three protomers of spike are colored in grey, blue, or purple respectively.

e. Surface representation of RBD epitope recognized by AZD1061. The epitope residues are indicated in different colors and labeled in black; the key residue K444 is labelled in red.

f. Interactions of AZD1061 paratope residues with the epitope. RBD is shown in the same surface representation and orientation as those in Fig. 2e. The paratope residues are shown in stick representation. The heavy chain is colored in yellow, and the light chain in orange. The key residue K444 is labelled in red.