FIG 2.
Structure of HPyV9 VP1 in complex with sialyloligosaccharides. (A) HPyV9 VP1 pentamer structure in complex with 3SLN. The pentamer is shown in cartoon representation, with one VP1 monomer highlighted in chocolate color and the other monomers shown in gray. The β strands (Anew, B to I) are labeled. 3SLN is drawn as a stick model and colored according to atom type (blue, nitrogens; red, oxygens; gold, carbons). One calcium ion is bound to each VP1 monomer, and the ions bound to the colored VP1 monomer are shown as green spheres, with the protein residues contacting it shown in stick representation. (B and C) Close-up views of the 3SLN (B) and 3GSLN (C) binding sites. HPyV9 VP1 and 3SLN are drawn as described for panel A, while the carbon atoms are colored yellow for 3GSLN. The view is adjusted to show more clearly the trisaccharide with the associated VP1 loops (the BC1, DE, and HI loops) of one monomer and the BC2 loop of the clockwise (cw) monomer. Composite-annealed omit difference density maps are shown contoured at 2.5σ around glycan at a 2.1-Å radius.