Figure 1. Sequence alignment of N2 reference, and three N1 sensitive mutants.

The sequence interval between the 121^th and 149^th amino acid (marked with - - - ; N2 reference numbering) is excluded from alignment for practical reasons. The relevant mutation sites are indicated in red. (r) - reference sequence; Number within the parenthesis indicate code for virus isolates according Table 2. (3) - H1N1 R118K mutant; (4) - H1N1 R118K/D151N mutant; (14) - H6N1 R118K/D151N/D198N mutant. Cl.Co- ClustalW consensus sequence, “*” is used to indicate identical residues, “:” is used to indicate conserved substitution, “.” is used to indicate semi-conserved substitution, “ ” (empty space) is used to indicate dissimilar residues.