FIG 1.

Structure of seal HA. (A) Overall structure, with one monomer HA highlighted in green (HA1 domain) and cyan (HA2 domain). Potential glycosylation sites are labeled, and those sites/glycans that could be visualized in the structure are shown as sticks (magenta). (B) Expanded view of the seal HA RBS with its three structural elements comprising the binding site—the 130 loop, the helix, and the 220 loop—colored yellow, red, and purple. Conserved residues are shown as sticks. (C) Comparison of the seal HA RBS (green) with overlapping equivalent structures from avian (cyan) and human (magenta) H3 HAs. Residue differences are shown as sticks. Seal HA is shown in cartoon form, while 3-SLN and interacting HA residues are shown as sticks. All structural figures were generated with MacPyMol (83).