Structural difference between the H1 and H5 or H3 HA in the binding pocket. The amino acid residues indicated on the HAs differ between the H1 (PR8) and H5 (A/Vietnam/1194/2004 (H5N1)) or H3 (A/Aichi/2/1968 (H3N2)) (PDB code: 3HMG) HAs around the region of the binding pocket for Stachyflin. For example, (N/D)-46 indicates that residue 46 in the HA2 is asparagine in H1, but aspartic acid in H5 (A) or H3 (B). (A) The structure and side chains of the H1 HA are in red, and those of the H5 HA are in green. The 2 structures were overlapped and compared. (B) The structure and side chains of the H3 HA are in blue. [(V/M)-115] indicates that residue 115 in the HA2, which is valine in H1, but methionine in H3, is not visible.