Protein Domain : Peptidase S30, polyprotein P1, potyvirus IPR002540

Type	Domain
Description	Proteolytic enzymes that exploit serine in their catalytic activity are ubiquitous, being found in viruses, bacteria and eukaryotes [ ]. They include a wide range of peptidase activity, including exopeptidase, endopeptidase, oligopeptidase and omega-peptidase activity. Many families of serine protease have been identified, these being grouped into clans on the basis of structural similarity and other functional evidence []. Structures are known for members of the clans and the structures indicate that some appear to be totally unrelated, suggesting different evolutionary origins for the serine peptidases [].Not withstanding their different evolutionary origins, there are similarities in the reaction mechanisms of several peptidases. Chymotrypsin, subtilisin and carboxypeptidase C have a catalytic triad of serine, aspartate and histidine in common: serine acts as a nucleophile, aspartate as an electrophile, and histidine as a base [ ]. The geometric orientations of the catalytic residues are similar between families, despite different protein folds []. The linear arrangements of the catalytic residues commonly reflect clan relationships. For example the catalytic triad in the chymotrypsin clan (PA) is ordered HDS, but is ordered DHS in the subtilisin clan (SB) and SDH in the carboxypeptidase clan (SC) [, ].The potyviridae are a family of positive strand RNA viruses, members of which include Zucchini yellow mosaic virus, and Turnip mosaic virus (strain Japanese) which cause considerable losses of crops worldwide.This entry represents a C-terminal region from various plant potyvirus P1 proteins (found at the N terminus of the polyprotein). The C terminus of P1 is a serine peptidase belonging to MEROPS peptidase family S30 (clan PA(S)). It is the protease responsible for autocatalytic cleavage between P1 and the helper component protease, which is a cysteine peptidase belonging to MEROPS peptidase family C6 [ , ]. The P1 protein may be involved in virus-host interactions [], and evasion of immune responses [].
Short Name	Pept_S30_P1_potyvir