FIG 5.

Structure of seal NA. (A) Overall structure of one NA monomer, looking down on the monomer, with the position of the enzyme active site indicated. While only one glycosylation site was occupied in the final structure (pink sticks), two others that are visible in this view are labeled and shown as sticks. The fourth position, Asn84, was substituted in the protein but would be at the back of this view. (B) NA active site, with highly conserved residues shown as sticks (labeled in black text). The amino acid substitutions between seal11 NA (green) and the avian N8 NA (cyan) are labeled and shown as sticks. The seal residue is indicated first in the labels and the avian residue second. (C and D) Exploded views of the enzyme active site with NA antivirals Ose (C) and Zan (D) bound. The NA residues that interact with each drug (dashed lines) are shown as sticks.