Family G2


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family G2

Family type peptidaseG02.001 - pre-neck appendage protein (Bacillus phage phi29) (bacteriophage phi-29), MEROPS Accession MER0151381 (peptidase unit: 692-854)
Content of familyPeptidase family G2 contains self-cleaving endopeptidases.
History Identifier created: MEROPS 9.5 (1 July 2011)
In bacteriophage phi29 there are 12 appendages attached to the neck region that are important for host cell recognition and entry. Neck-appendage proteins from Bacillus phages, tail spike proteins from coliphages and K5 lyases are all homotrimers. Prior to trimerization, each subunit is autolytically processed to release its C-terminal domain (Schwarzer et al., 2007). The C-terminal domain acts as chaperone, assisting in the folding and assembly of the phage proteins.
Catalytic typeGlutamic
Active site residuesD692 E695 
Active siteIn the self-processing of the tail spike protein of bacteriophage phi29, Glu695 from one chain is thought to activate a water molecule, which attacks the peptide bond Trp690+Ser on another chain (Schulz & Ficner, 2011). Self-cleavage is thus in trans.
Molecular structureThe tertiary structures of bacteriophage phi29 neck appendage protein before and after processing have been solved (Xiang et al., 2009). The fold is unique and is thus the type example for clan GB.
Distribution of family Bacteria details  
Archaea -  
Protozoa -  
Fungi -  
Plants -  
Animals details  
Viruses details  
Biological functionsSelf-cleavage is important for correct assembly of the viral appendages.
Statistics for family G2Sequences:128
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
pre-neck appendage protein (Bacillus phage phi29)G02.001Yes
family G2 non-peptidase homologuesnon-peptidase homologue-
family G2 unassigned peptidasesunassigned-