|Family type peptidase||N05.001 - picobirnavirus self-cleaving protein (Human picobirnavirus), MEROPS Accession MER0202949 (peptidase unit: 1-552)|
|Content of family||Family N5 includes self-cleaving endopeptidases|
Identifier created: MEROPS 9.3 (7 September 2010)|
Picobirnaviruses are double-stranded RNA viruses. The virus particle is organized around a central icosahedral core capsid consisting of 120 identical subunits (Duquerroy et al., 2009). Each subunit undergoes an autoproteolytic cleavage, releasing a peptide that remains in the capsid associated with the RNA. Autoproteolytic cleavages of asparaginyl bonds are known also for capsid and coat proteins from nodaviruses (N1), tetraviruses (N2), reoviruses (N7) and picornaviruses (N8).
|Active site residues||N45 |
|Active site||Cleavage occurs at Asn45, and this is assumed to be the nucleophile. In the nodavirus and tetravirus coat protein an active site dimer exists, in which the other component is an aspartate or glutamate. No equivalent residue in the picobirnavirus has been identified.|
|Activities and specificities||The only peptidase activity is release of an N-terminal 44-residue peptide from the N-terminus of the coat protein.|
|Molecular structure||The tertiary structure of the cleaved rabbit picobirnavirus coat protein (N05.001) has been solved, the structure is unrelated to that of any other peptidase and the rabbit picobirnavirus coat protein is the type structure for clan NE. The The mature N-terminus is a beta-hairpin more than 20 angstroms distant from the globular domain that comprises the rest of the molecule. In the crystal structure the N-terminal beta-hairpin of one monomer is embedded within the second monomer of the dimer. The released peptide is not visible in the solved tertiary structure but remains within the viral capsid associated with the RNA (Duquerroy et al., 2009).|