| Primary Identifier | IPR025773 | Type | Domain |
| Short Name | AV_PCPbeta |
| description | Arteriviruses are enveloped, positive-stranded RNA viruses and includepathogens of major economic concern to the swine- and horse-breedingindustries: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 beexpressed only by ribosomal frameshifting, yelding a 1ab fusion protein. Bothreplicase gene products are multidomain precursor proteins which areproteolytically processed into functional nonstructural proteins (nsps) by acomplex proteolytic cascade that is directed by four (PRRSV/LDV) or three(EAV) proteinase domains encoded in ORF1a. The arterivirus replicaseprocessing scheme involves the rapid autoproteolytic release of two or threeN-terminal nsps (nsp1 (or nsp1alpha/1beta) and nsp2) and thesubsequent processing of the remaining polyproteins by the "main protease"residing in nsp4, together resulting in a set of 13or 14 individual nsps. The arterivirus nsp1 region contains a tandem ofpapain-like cysteine autoprotease domains (PCPalpha and PCPbeta), but in EAVPCPalpha has lost its enzymatic activity, resulting in the 'merge' ofnsp1alpha and nsp1beta into a single nsp1 subunit. Thus, instead of threeself-cleaving N-terminal subunits, EAV has two: nsp1 and nsp2. The PCPalphaand PCPbeta domains mediate the nsp1alpha|1beta and nsp1beta|2 cleavages,respectively. The catalytic dyad of PCPalpha and PCPbeta domains is composedof Cys and His residues. In EAV, a Lys residue is found in place of thecatalytic Cys residue, which explains the proteolytic deficiency of the EAVPCPalpha domain [, , , ]. The PCPalpha and PCPbeta domains form respectivelypeptidase families C31 and C32.The PCPalpha and PCPbeta domains have a typical papain fold, which consists ofa compact global region containing sequentially connected left (L) and right(R) parts in a so-called standard orientation. The L subdomain of PCPalphaconsists of four α-helices, while the R subdomain is formed by threeantiparallel beta strands []. The L subdomain of the PCBbetaconsists of three α-helices, while the R subdomain is formed by fourantiparallel β-strands []. The Cys and His residues faceeach other at the L-R interface and form the catalytic centre of the PCPalphaand PCPbeta domains [, ].This entry represents the PCPbeta domain (peptidase C32). |
