Family C21


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family C21

NamePeptidase family C21 (tymovirus endopeptidase family)
Family type peptidaseC21.001 - tymovirus peptidase (turnip yellow mosaic virus), MEROPS Accession MER0000879 (peptidase unit: 773-874)
Content of familyPeptidase family C21 contains polyprotein processing endopeptidases from the single-stranded RNA viruses related to turnip yellow mosaic virus (tymoviruses).
History Identifier created: Methods Enzymol. 244:461-486 (1994)
The proteolytic maturation of turnip yellow mosaic virus (TYMV) was descibed by Morch et al., 1989.
Catalytic typeCysteine
Active site residuesC783 H869 
Active siteTwo active site residues (Cys, His) have been identified by site-directed mutagenesis (Bransom & Dreher, 1994) (see the Alignment).
Activities and specificitiesIn TYMV, cleavage of the 206-kDa polyprotein occurs in cis at a AlaThr bond, releasing 150-kDa and 70-kDa proteins, has been demonstrated in vitro. There appears to be an extended specificity site with residues in P4, P3 and P2 also important for cleavage (Bransom et al., 1996). The only evidence that this cleavage occurs in vivo comes from the immunological detection of the 70-kDa polyprotein in tobacco leaves (Prodhomme et al., 2004). The cleavage site is not well conserved between tymoviruses.
InhibitorsInhibition has been reported with N-ethylmaleimide, which inhibits most cysteine peptidases (Morch et al., 1989).
Molecular structureThe endopeptidase has not been isolated and its extent within the polyprotein is not known with certainty. No tertiary structure has been determined.
Basis of clan assignmentActive site residues for members of this family and family C1 occur in the same order in the sequence: C, H.
Distribution of family Bacteria -  
Archaea -  
Protozoa -  
Fungi -  
Plants -  
Animals -  
Viruses details  
Biological functionsThe single cleavage releases the C-terminal RNA polymerase.
ReviewsRozanov (2004)
Statistics for family C21Sequences:33
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
tymovirus peptidaseC21.001Yes
family C21 unassigned peptidasesunassigned-