Peptidase_C32 |
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PFAM accession number: | PF05411 |
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Interpro abstract (IPR025773): | Arteriviruses are enveloped, positive-stranded RNA viruses and include pathogens of major economic concern to the swine- and horse-breeding industries:
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 [ (PUBMED:7769711) (PUBMED:10725411) (PUBMED:11172046) (PUBMED:20696193) ]. The PCPalpha and PCPbeta domains form respectively 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 [ (PUBMED:19706710) ]. The L subdomain of the PCBbeta consists of three alpha-helices, while the R subdomain is formed by four antiparallel beta-strands [ (PUBMED: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 [ (PUBMED:19706710) (PUBMED:20410261) ]. This entry represents the PCPbeta domain (peptidase C32). |
GO function: | cysteine-type peptidase activity (GO:0008234) |
This is a PFAM domain. For full annotation and more information, please see the PFAM entry Peptidase_C32