Extended Data Fig. 3: Analysis of the M1 structure determined within virions and VLPs.
From: The native structure of the assembled matrix protein 1 of influenza A virus
a, Overlay of the model of M1 subunits as they are arranged in virions and VLPs with two neighbouring M1 NTD domains (pink) within the crystal packing in PDB 1EA313. Inset highlights the positions of the interhelix loops (L). b, Model of M1 subunits as they are arranged in virions and VLPs, shown in three different orientations (as in Fig. 2b). c, Surface charge representation for the NTD in equivalent orientations to those shown in a, coloured from negative (red) to positive (blue). Charged residues that form interstrand interfaces, and their respective helix numbers, are marked in the top and bottom panels. Basic residues shown in Fig. 2c and involved in membrane interaction are marked in the middle panel. Mutation of residues 77 and 78 to alanine reduces M1 incorporation into virions63. d, Overlay of the M1 model with two neighbouring infectious salmon anaemia virus matrix proteins (magenta) from the crystal packing in PDB 5WCO15. The difference in orientation of the CTD could reflect differences in influenza A virus or infectious salmon anaemia virus virion morphology, but we consider it more likely that it reflects the sequence divergence between infectious salmon anaemia virus and influenza A virus.
