Family N7


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family N7

Family type peptidaseN07.001 - reovirus type 1 coat protein (Mammalian orthoreovirus 1), MEROPS Accession MER0191303 (peptidase unit: 2-708)
Content of familyFamily N7 includes self-cleaving endopeptidases
History Identifier created: MEROPS 9.3 (7 September 2010)
Reoviruses are double-stranded DNA viruses. The virus particle consists of two concentric, icosahedral protein capsids surrounding a ten segment, double-stranded RNA genome (Zhang etal, 2005). One of the capsid proteins, known as mu-1, undergoes an autoproteolytic cleavage, releasing a peptide that remains in the capsid associated with the RNA. Similar autoproteolytic cleavages are known for coat proteins from nodaviruses (family N1), tetraviruses (N2), picobirnaviruses (N5) and picornaviruses (N8).
Catalytic typeAsparagine
Active site residuesN42 
Active siteCleavage occurs at Asn42, and this is assumed to be the nucleophile. Substitution of Asn42 prevents cleavage (Odegard et al., 2004). Presumably, by analogy to other coat proteins a second residue is required to form a catalytic dyad, which is Asp in the nodavirus coat protein (N01.001) or Glu in the tetravirus coat protein (N02.001).
Activities and specificitiesThe only peptidase activity is release an N-terminal 42-residue peptide from the N-terminus of the coat protein.
Molecular structureThe mu-1 protein is myristoylated at its N-terminus. The tertiary structure of the cleaved mu-1 protein has been solved and shows a fold unrelated to that of any other peptidase (Zhang et al., 2005). The structure of the mu-1 protein is therefore the type structure for clan NC.
Distribution of family Bacteria -  
Archaea -  
Protozoa -  
Fungi -  
Plants -  
Animals -  
Viruses details  
Biological functionsThe peptide released by cleavage of mu-1 i s known as mu-1N. A second cleavage by an unknown, exogenous peptidase releases a peptide known as phi from the C-terminus (the cleavage site has not been determined). Both mu-1N and phi are myristoylated and associate with host erythrocyte membranes where both contribute to pore formation and ultimately to membrane penetration by virus particles (Ivanovic et al., 2008).
Statistics for family N7Sequences:22
Identifiers with PDB entries:1
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
reovirus type 1 coat proteinN07.001Yes
aquareovirus coat proteinN07.002-
family N7 unassigned peptide lyaseunassigned-