Family C37


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family C37

Family type peptidaseC37.001 - calicivirin (Southampton virus), MEROPS Accession MER0002195 (peptidase unit: 1100-1272)
Content of familyPeptidase family C37 contains calicivirin, a polyprotein-processing endopeptidases known from caliciviruses.
History Identifier created: Perspect.Drug Discov.Des. 6:1-11 (1996)
Each virus in the calicivirus group of the picornaviruses encodes just a single peptidase in the ORF1 polyprotein, either of family C24 or C37. The function of the family calicivirin (C37.001) in Southampton virus was discovered by Martin Alonso et al. (1996) and further characterised by Liu et al. (1999). .
Catalytic typeCysteine
Active site residuesH1129 C1238 
Active siteThe two essential catalytic residues are numbered His1129 and Cys1238 by MEROPS (see the Alignment). Cys1238 can be replaced by Ser without loss of activity. The highly-conserved Glu1153 between the two catalytic residues is not essential, being replaced by alanine without loss of activity (Someya et al., 2002; Nakamura et al., 2005).
Activities and specificitiesP1 residues in the cleavage sites are commonly Glu or Gln, as for several other families in clan PA(C). The mechanism of substrate binding has been considered in the light of the structure of the Chiba virus peptidase (Nakamura et al., 2005).
Molecular structureThe structure of the peptidase (C37.001) from Chiba virus has been described (Nakamura et al., 2005). The chymotrypsin-like fold resembles those of other viral peptidases in subclan PA(C).
Basis of clan assignmentPredicted active site residues for members of this family and family S1 occur in the same order in the sequence: H, E/D, C/S.
Distribution of family Bacteria -  
Archaea -  
Protozoa -  
Fungi -  
Plants -  
Animals -  
Viruses details  
Biological functionsThought to be responsible for all of the processing reactions in the ORF1 polyproteins of the caliciviruses that encode the enzyme, including Southampton virus and Norwalk virus (Myers et al., 2004).
ReviewsNakamura et al. (2005)
Statistics for family C37Sequences:37
Identifiers with PDB entries:2
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
murine norovirus NS6 peptidaseC37.003Yes
non-peptidase homologue-
family C37 unassigned peptidasesunassigned-