{PDOC51276}
{PS51276; PEPTIDASE_C56_PFPI}
{BEGIN}
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* PfpI endopeptidase domain profile *
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Pyrococcus  furiosus  protease  I  (PfpI)  (EC  3.2.-.-)  is  an intracellular
cysteine  peptidase,  characterized by its stability and proposed to represent
the  predominant  proteolytic  activity  of this thermophilic archaebacterium.
Pfpi-like proteins have been found in bacteria, archaea, in some plants and in
amoebas.

The  structure  of P. horikoshii PfpI shows an alpha/beta sandwich fold, which
consists of a central beta sheet flanked by two helices and two strands on one
side,  and  by six helices and two strands on the other side (see <PDB:1G2I>).
The  fold  resembles  that of glutamine amidotransferases (GATase) of class I,
which   are   characterized  by  a  conserved  Cys-His-Glu  active  site  (see
<PDOC00405>). The catalytically essential cysteine is located at a nucleophile
elbow. PfpI forms a hexameric structure and the active sites are formed at the
interfaces  between  three  pairs of monomers. Cys and His form a triad with a
glutamate  residue from an adjacent monomer [1]. Pfpi endopeptidases belong to
the  peptidase  C56  family,  which  is  classified  with  the  peptidase  C26
gamma-glutamyl  hydrolases (see <PDOC51275>) in the clan PC(C) [E1, E2]. Other
peptidase C56 family proteins are structurally and functionally different [2],
e.g. human DJ-1 creates a hydrophobic patch at the molecular interface instead
of  completing  the  catalytic  triad,  while  E. coli chaperone HSP31 forms a
Cys-His-Asp triad.

Some proteins known to contain a PfpI endopeptidase domain:

 - Pyrococcus  furiosus  intracellular  protease 1 (PfpI), an ATP-independent,
   highly thermically and chemically stable endopeptidase.
 - Pyrococcus horikoshii intracellular   protease   1   (PfpI/PH1704).
 - Bacillus subtilis general stress protein 18 (GSP18).
 - Escherichia coli protein yhbO.

The profile we developed covers the entire PfpI endopeptidase domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Note: These proteins belong to family C56 in the classification of peptidases
 [E1,E2].
-Note:  The PfpI endopeptidase domain profile is in competition with a profile
 of a related domain, i.e. GATase type 1 (see <PDOC00405>).

-Last update: December 2006 / First entry.

[ 1] Du X., Choi I.-G., Kim R., Wang W., Jancarik J., Yokota H., Kim S.-H.
     "Crystal structure of an intracellular protease from Pyrococcus
     horikoshii at 2-A resolution."
     Proc. Natl. Acad. Sci. U.S.A. 97:14079-14084(2000).
     PubMed=11114201; DOI=10.1073/pnas.260503597
[ 2] Bandyopadhyay S., Cookson M.R.
     "Evolutionary and functional relationships within the DJ1
     superfamily."
     BMC Evol. Biol. 4:6-6(2004).
     PubMed=15070401; DOI=10.1186/1471-2148-4-6
[E1] https://www.uniprot.org/docs/peptidas
[E2] https://www.ebi.ac.uk/merops/cgi-bin/merops.cgi?id=C56

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