Domain

Arterivirus papain-like cysteine protease alpha (PCPalpha) domain (IPR008741)

Short name: AV_PCPalpha

Domain relationships

None.

Description

Arteriviruses are enveloped, positive-stranded RNA viruses and include pathogens of major economic concern to the swine- and horse-breeding industries:

  • Equine arteritis virus (EAV).
  • Porcine reproductive and respiratory syndrome virus (PRRSV).
  • Mice actate dehydrogenase-elevating virus.
  • Simian hemorrhagic fever virus.

The arterivirus replicase gene is composed of two open reading frames (ORFs). ORF1a is translated directly from the genomic RNA, whereas ORF1b can be expressed only by ribosomal frameshifting, yelding a 1ab fusion protein. Both replicase gene products are multidomain precursor proteins which are proteolytically processed into functional nonstructural proteins (nsps) by a complex proteolytic cascade that is directed by four (PRRSV/LDV) or three (EAV) proteinase domains encoded in ORF1a. The arterivirus replicase processing scheme involves the rapid autoproteolytic release of two or three N-terminal nsps (nsp1 (or nsp1alpha/1beta) and nsp2) and the subsequent processing of the remaining polyproteins by the "main protease" residing in nsp4, together resulting in a set of 13 or 14 individual nsps.

The arterivirus nsp1 region contains a tandem of papain-like cysteine autoprotease domains (PCPalpha and PCPbeta), but in EAV PCPalpha has lost its enzymatic activity, resulting in the 'merge' of nsp1alpha and nsp1beta into a single nsp1 subunit. Thus, instead of three self-cleaving N-terminal subunits, EAV has two: nsp1 and nsp2. The PCPalpha and PCPbeta domains mediate the nsp1alpha|1beta and nsp1beta|2 cleavages, respectively. The catalytic dyad of PCPalpha and PCPbeta domains is composed of Cys and His residues. In EAV, a Lys residue is found in place of the catalytic Cys residue, which explains the proteolytic deficiency of the EAV PCPalpha domain [PMID: 7769711, PMID: 10725411, PMID: 11172046, PMID: 20696193]. The PCPalpha and PCPbeta domains form respectively MEROPS peptidase families C31 and C32.

The PCPalpha and PCPbeta domains have a typical papain fold, which consists of a compact global region containing sequentially connected left (L) and right (R) parts in a so-called standard orientation. The L subdomain of PCPalpha consists of four alpha-helices, while the R subdomain is formed by three antiparallel beta strands [PMID: 19706710]. The L subdomain of the PCBbeta consists of three alpha-helices, while the R subdomain is formed by four antiparallel beta-strands [PMID: 20410261]. The Cys and His residues face each other at the L-R interface and form the catalytic centre of the PCPalpha and PCPbeta domains [PMID: 19706710, PMID: 20410261].

This entry represents the PCPalpha domain (peptidase C31).

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0004197 cysteine-type endopeptidase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

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