| Primary Identifier | IPR024387 | Type | Domain |
| Short Name | Pept_C3G_Picornavir |
| description | Viruses in the order Picornavirales infect different vertebrate, invertebrate, and plant hosts and are responsible for a variety of human, animal, and plant diseases. These viruses have a single-stranded, positive sense RNA genome that generally translates a large precursor polyprotein which is proteolytically cleaved after translation to generate mature functional viral proteins. This process is usually mediated by (more than one) proteases, and a 3C (for the family Picornaviridae) or 3C-like (3CL) protease (for other families) plays a central role in the cleavage of the viral precursor polyprotein. In addition to this key role, 3C/3C-like protease is able to cleave a number of host proteins to remodel the cellular environment for virus reproduction [, , , , , ]. The Picornavirales 3C/3C-like protease domain forms the MEROPS peptidase family C3 (picornain family) of clan PA.The 3C/3CL protease domain adopts a chymotrypsin-like fold with a cysteine nucleophile in place of a commonly found serine which suggests that the cysteine and serine perform an analogous catalytic function. The catalytic triad is made of a histidine, an aspartate/glutamate and the conserved cysteine in this sequential order. The 3C/3CL protease domain folds into two antiparallel beta barrels that are linked by a loop with a short α-helix in its middle, and flanked by two other α-helices at the N- and C-terminal. The two barrels are topologically equivalent and are formed by six antiparallel beta strands with the first four organised into a Greek key motif. The active-site residues are located in the cleft between the two barrels with the nucleophilic Cys from the C-terminal barrel and the general acid base His-Glu/Asp from the N-terminal barrel [, , ].This entry represents a rice tungro spherical waikavirus-type peptidase that belongs to MEROPS peptidase family C3G. It is a picornain 3C-type protease, and is responsible for the self-cleavage of the positive single-stranded polyproteins of a number of plant viral genomes. The location of the protease activity of the polyprotein is at the C-terminal end, adjacent and N-terminal to the putative RNA polymerase [, ]. |
