Peptidase C30/C16 (IPR013016)

Short name: Peptidase_C30/C16

Overlapping homologous superfamilies


Domain relationships


This entry contains coronavirus cysteine endopeptidases that belong to MEROPS peptidase families C30 (clan PA) and C16 (subfamiles C16A and C16B, clan CA). These peptidases are involved in viral polyprotein processing. All coronaviruses encode between one and two accessory cysteine proteinases that recognise and process one or two sites in the amino-terminal half of the replicase polyprotein during assembly of the viral replication complex. MHV, HCoV and TGEV encode two accesssory proteinases, called coronavirus papain-like proteinase 1 and 2 (PL1-PRO and PL2-PRO). IBV and SARS encodes only one called PL-PRO [PMID: 10725411]. Coronavirus papain-like proteinases 1 and 2 have restricted specificities, cleaving respectively two and one bond(s)in the polyprotein. This restricted activity may be due to extended specificity sites: Arg or Lys at the cleavage site position P5 are required for PL1-PRO [PMID: 8396668], and Phe at the cleavage site position P6 is required for PL2-PRO [PMID: 12805436]. PL1-PRO releases p28 and p65 from the N terminus of the polyprotein; PL2-PRO cleaves between p210 and p150.

The peptidase family C16 domain is about 260 amino acids in length. This domain is predicted to have an alpha-beta structural organisation known as the papain-like fold. It consists of three alpha-helices and three strands of antiparallel beta-sheet [PMID: 10329692]. This domain has a catalytic dyad consisting of a Cys and a downstream His [PMID: 10725411, PMID: 8396668, PMID: 10329692]. The nucleophilic Cys occurs in the motif Asn-Cys-Xaa-Yaa in which Xaa is an aromatic, hydrophobic residue and Yaa is an aliphatic hydrophobic amino acid. There is little conservation around the general base His. This peptidase domain also contains Cys residues involved in the formation of a zinc-binding finger which connects the left and right hand domains of a papain-like fold, and may be involved in substrate binding or control the movement of the catalytic domain [PMID: 10329692].

GO terms

Biological Process

GO:0006508 proteolysis

Molecular Function

GO:0003968 RNA-directed 5'-3' RNA polymerase activity
GO:0008234 cysteine-type peptidase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE profiles