Family C30


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family C30

Family type peptidaseC30.004 - porcine transmissible gastroenteritis virus-type main peptidase (transmissible gastroenteritis virus), MEROPS Accession MER0002860 (peptidase unit: 2879-3180)
Content of familyFamily C30 contains endopeptidases from coronaviruses.
History Identifier created: Perspect.Drug Discov.Des. 6:1-11 (1996)
Following the study of the murine hepatitis coronavirus genome (Lee et al., 1991) it has become clear that the coronaviruses encode picornain-like peptidases (family C30, clan PA) and commonly also papain-like peptidases (family C16, clan CA).
Catalytic typeCysteine
Active site residuesH2919 C3022 
Active siteThe active site residues of the peptidases of family C30 are a His and a Cys, which form a catalytic dyad (see the Alignment).
Activities and specificitiesEndopeptidases of family C30 are polyprotein processing. The specificity of the 3C-like peptidase is highly conserved among coronaviruses (Ziebuhr et al., 2000; Hegyi & Ziebuhr, 2002). There is a requirement for Gln at position P1 (Tibbles et al., 1996), whilst P1" may be occupied by small aliphatic residues. At position P2 Leu is usually found, but may be Ile, Tyr, Val, Phe or Met. P4 may contain Val, Ala, Ser or Tyr.
InhibitorsThe most detailed information about inhibitors of family C30 peptidases relates to the peptidase (C30.005) of the SARS coronavirus. This is a major drug target, and work towards inhibitors that could have therapeutic use has been reviewed by Liang (2006).
Molecular structureAs can be seen from the Structure pages for C30.003, C30.004 and C30.005, the tertiary structures of peptidases in family C30 consist of three domains. The first two contain anti-parallel beta barrels, with the third consisting of an arrangement of alpha-helices. The catalytic residues are found in a cleft between the first two domains. This structure is characteristic of clan PA.
Basis of clan assignmentActive site residues for members of this family and family S1 occur in the same order in the sequence: H, C/S.
Distribution of family Bacteria -  
Archaea -  
Protozoa -  
Fungi -  
Plants -  
Animals -  
Viruses details  
Biological functionsDuring viral replication, the viral peptidases, polymerase and helicase of the coronavirus are expressed as a polyprotein with a number of putative picornain 3C-like endopeptidase cleavage sites. Processing of the polyprotein by 3C-like endopeptidase liberates active forms of the viral replicase proteins. Processing is required throughout the infection cycle, and therefore, the role of 3C-like endopeptidase is critical in viral replication (Kim et al., 1995).
Pharmaceutical and biotech relevanceThe SARS virus 3C-like endopeptidase (C30.005) is a target for the treatment of severe acute respiratory syndrome (SARS).
ReviewsZiebuhr et al. (2000); Denison (2004)
Statistics for family C30Sequences:96
Identifiers with PDB entries:5
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
coronavirus picornain 3C-like peptidase-1C30.001-
avian infectious bronchitis coronavirus 3C-like peptidaseC30.002Yes
human coronavirus 229E main peptidaseC30.003Yes
porcine transmissible gastroenteritis virus-type main peptidaseC30.004Yes
SARS coronavirus picornain 3C-like peptidaseC30.005Yes
MERS coronavirus picornain 3C-like peptidaseC30.006-
family C30 unassigned peptidasesunassignedYes