Fig. 3.

Sequence alignment between the COOH-terminal region of the PA subunit of the RNA-dependent RNA polymerase of a H5N1 avian influenza virus (NCBI accession number: AAV48550), and the first two domains of the severe acute respiratory syndrome coronavirus (SARS-CoV) main protease (3CL^pro; NCBI accession number: P59641). The alignment was generated using the CLUSTALW software (http://npsa-pbil.ibcp.fr/cgi-bin/npsa_automat.pl?page=npsa_clustalw.html). The boxes evidence the perfect alignment between the catalytic His₄₁ and Cys₁₄₅ of SARS-CoV 3CL^pro and the putatively catalytic His₅₁₀ and Cys₁₄₅ of influenza A PA.