Family N1


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family N1

Family type peptidaseN01.001 - nodavirus peptide lyase (flock house virus), MEROPS Accession MER0000991 (peptidase unit: 1-407)
Content of familyPeptidase family A6 contains an endopeptidase.
History Identifier created: MEROPS 9.3 (7 September 2010)
The structure of black beetle nodavirus (Hosur et al., 1987) showed that proteins beta and gamma are derived from protein alpha by cleavage of an AsnAla bond, the cleavage that is mediated by the nodavirus endopeptidase (N01.001).
Catalytic typeAsparagine
Active site residuesD75 N363 
Active siteThe active site residues are believed to be Asp75 and Asn363, the latter being the P1 residue in the cleavage site.
Activities and specificitiesThe only known activity is an autolytic cleavage of Asn363Ala364 releasing a 44-residue C-terminal fragment. The reaction is very slow (t0.5 = 4 h), and only occurs within the assembled virion. Therefore each active site functions only once and there is no turnover. Divalent metal ions bind to the surface interfaces and help apply stress to the scissile bond, but are not involved directly in the cleavage (Reddy et al., 2004). The liberated 44-residue polypeptide (known as the gamma peptide) remains internally associated with the virion.
InhibitorsNo inhibitors are known.
Molecular structureThe tertiary structure of the black beetle nodavirus has been solved (Wery et al., 1994). The virion is an icosahedron containing 60 triangular coat protein units, each unit consisting of three proteins. The coat protein consists of two domains, an eight-stranded beta-barrel on the surface and a three-helix bundle on the inner face. The fold is similar to those of other viral coat proteins, including coat proteins of tetraviruses (family N2) which undergo a similar cleavage, although the catalytic Asp is replaced with Glu.
Basis of clan assignmentType family of clan NA.
Distribution of family Bacteria -  
Archaea -  
Protozoa -  
Fungi -  
Plants -  
Animals -  
Viruses details  
Biological functionsThe peptidases in family N1 are the coat proteins from nodaviruses, single-stranded RNA viruses that infect insects, fish and mammals. The coat protein precursor undergoes slow, autolytic maturation. Cleavage of the coat protein helps stabilize the virion and is an important stage in maturation of the virus. The gamma-peptide is eventually released to interact with the endosomal membrane following endocytosis of the virus particle by host cells.
ReviewsReddy et al., 2004
Statistics for family N1Sequences:8
Identifiers with PDB entries:2
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
nodavirus peptide lyaseN01.001Yes
family N1 unassigned peptide lyasesunassignedYes