Figure 2.

P22 Interactions with CD33

(A) The chemical structures of 3′-sialyllactose, 6′-sialyllactose, and P22 from left to right, respectively. The sialic acid moiety of the three ligands is shown in the same view.

(B) Close-up view of the CD33 residues (gray sticks) directly interacting with P22 (yellow sticks). Residues making hydrophobic interactions with P22 are overlayed with a semi-transparent molecular surface.

(C) The extended polar contact network (green dashes) P22 makes with the F- and G-strands of CD33.

(D and E) (D) 3′-sialyllactose and (E) 6′-sialyllactose binding to the key CD33 R119 residue. The sialic acid moiety of the ligand is shown in yellow and the galactopyranosyl ring in green. Polar contacts between the ligand and CD33 are indicated by the green dashes. In both the 3′- and 6′-sialyllactose complexes with CD33, the glucopyranosyl ring is not visible (PDB: 5J06 and 5J0B).

See also Figures S1, S2, and S4 and Table S2.