Amino acid mutations differences in the NA of influenza virus isolates in Japan, 2009–2010 and 2010–2011.

<p>Three-dimensional structures of monomeric NA were downloaded from the Protein Data Bank (RCSB PDB, <a href="http://www.pdb.org" target="_blank">http://www.pdb.org</a>) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036455#pone.0036455-Berman1" target="_blank">[44]</a> and visualized using PyMol (<a href="http:www.pymol.org" target="_blank">http:www.pymol.org</a>). The top view of the NA is shown. (A) The amino acid differences between A(H1N1)pdm09 isolates in Japan and vaccine strain, A/California/07/2009 were compared. Amino acid substitutions V241I and N369K are shown in yellow. These amino acid changes are located outside the antigenic sites but are phylogenetically relevant. PDB entry: 3NSS. (B) Antigenic site mutations between Japanese A(H3N2) isolates and vaccine strain, A/Perth/16/2009 were compared. L338F mutation is located in antigenic site F’ (olive); K369T is localized in antigenic site I’; and R400K and N402D are located in antigenic site K’. PDB entry: 1IVG (C) Amino acid substitutions in the NA antigenic sites of Japanese influenza B isolates and vaccine strain, B/Brisbane/60/2008 were compared. Mutations at N329D is localized at antigenic site F’ (olive); and D340N/D is located in antigenic site G’ (violet). PDB entry: 1INF.