TABLE 2.

Sequence alignment of subtypes H1 to H18 with PDB IDs and UniProtKB accession numbers^c

^aHighly conserved His183 is involved in receptor binding.

^bSubtype-specific residues at positions 216 and 231 potentially influence the pK_a of His184.

^cHA subtypes are listed in alphabetical order. Important residues at the HA1-HA1 interface are shown in boldface. Residues forming the conserved interactions at the HA1-HA1 interface are highlighted.