FIG 1.

Amino acid plasticity at residue 145. (A) Publicly available H3 HA sequences were retrieved, and the relative frequencies of identified amino acids at residue 145 were calculated for swine, human, avian, canine, and equine AIVs. Amino acids present at frequency below 1% are not labeled in the figure. (B) Schematic representation of the HA gene segment of A/turkey/Ohio/313053/2004 (H3N2), depicting the codon corresponding to residue 145 and respective amino acid substitutions introduced by site-directed mutagenesis. (C) HA monomeric structure of A/turkey/Ohio/313053/2004 (H3N2), indicating the location of HA residue 145.