|Family type peptidase||S80.001 - prohead peptidase gp175 (Pseudomonas aeruginosa phage phiKZ) (Pseudomonas phage phiKZ), MEROPS Accession MER0221018 (peptidase unit: 1-270)|
|Content of family|
Identifier created: MEROPS 9.7 (1 August 2012)|
The Pseudomonas aeruginosa phage phiKZ is unusual amongst double-stranded DNA viruses because the genome is very large (280 kb) and encodes a variety of proteins that are remarkably divergent from those of other viruses. The large virion head, composed of 1560 copies of the coat protein, contains not only the viral DNA but also a large, cylindrical protein complex known as the 'inner body', around which the viral DNA is wrapped. Some proteins are present in both the head and the inner body. Maturation of the viral prohead involves 39 cleavages in at least 19 of the prohead proteins, and the product of the gp175 gene has been identified, initially by bioinformatics, as the peptidase responsible for all of these cleavages (Thomas et al., 2012). Recombinant Gp175 expressed in E. coli processed the Gp93 precursor to the protein equivalent in size to mature Gp93 (Thomas et al., 2012).
|Active site residues||H89 S168 |
|Active site||A His/Ser catalytic dyad has been predicted from comparison with the known catalytic residues in the T4 prohead protease Gp21 (Thomas et al., 2012).|
|Activities and specificities||Analysis of the known cleavage sites has identified a common recognition motif, (Ser/Ala/Gly)-Xaa-Glu+, which is similar to the recognition motif in T4 prohead protease Gp21 (S77.001; Thomas et al., 2012).|
|Molecular structure||The T4 prohead protease Gp21 is synthesized as a precursor with a C-terminal propeptide, and the Gp175 peptidase may also be synthsized as a precursor, activated by removal of a C-terminal propeptide by self-cleavage at Glu210 (Thomas et al., 2012). No tertiary structure for any member of family S80 has been solved, but from the distant sequence relationship to family S77, family S80 is included in clan SH.|