Family S62


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family S62

Family type peptidaseS62.001 - influenza A PA peptidase (influenza A virus), MEROPS Accession MER0029886 (peptidase unit: 168-716)
Content of familyPeptidase family S62 contains viral endopeptidases.
History Identifier created: MEROPS 6.5 (22 December 2003)
Endopeptidase activity is associated with the “PA domain” of the influenza virus RNA polymerase, and also has endonuclease activity (Hara et al., 2001; Fodor et al., 2002). 'PA' is an abbreviation for 'polymerase acidic protein'. The influenza virus RNA polymerase is a multifunctional protein, consisting of three subunits. Subunit PB1 is the polymerase; subunit PB2 is a cap-binding protein important for the initiation of viral mRNA synthesis; and the third subunit is PA (S62.001).
Catalytic typeSerine
Active site residuesS624 
Active siteApart from the active site serine, which has been identified by site-directed mutagenesis and by labelling with DFP (Hara et al., 2001), the active site of the PA protein is unknown. Several additional residues have been shown by site-directed mutagenesis to affect endonuclease activity, including His510 (Fodor et al., 2002) and Arg638 (Fodor et al., 2003). Mutations of Cys453 can compensate for the attenuated viral growth and production of defective, interfering RNAs caused by Arg638 mutants (Fodor et al., 2003). A catalytic triad comprising His510, Asp547 and S624 has been proposed (Hara et al., 2001).
Activities and specificitiesInfluenza A PA peptidase has been shown to cleave the chymotrypsin substrate Suc-Leu-Leu-Val-Tyr-NHMec and casein (Hara et al., 2001).
InhibitorsDFP has been shown to be inhibitory (Hara et al., 2001) confirming that PA protein is a serine peptidase.
Molecular structure
Distribution of family Bacteria details  
Archaea -  
Protozoa -  
Fungi -  
Plants -  
Animals details  
Viruses details  
Biological functionsThe peptidase is not essential but its absence reduces viral growth (Toyoda et al., 2003). PA has been shown to interact with the matrix protein M1 (Hara et al., 2003).
Statistics for family S62Sequences:56
Identifiers with PDB entries:1
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
influenza A PA peptidaseS62.001Yes
family S62 non-peptidase homologuesnon-peptidase homologue-
family S62 unassigned peptidasesunassigned-