{PDOC51443}
{PS51443; PCS}
{BEGIN}
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* Phytochelatin synthase (PCS) domain profile *
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Phytochelatins (PCs) are well known as the heavy metal-detoxifying peptides in
higher plants,  eukaryotic  algae,  fungi,  nematode  and cyanobacteria. These
peptides, of  the  general  structure  (gamma-Glu-Cys)n-Gly (with n=2-11), are
enzymatically synthesized  from  the  substrate  glutathione  (GSH).  PCs  are
synthesized posttranslationally  by  the  PC  synthase  (PCS) (EC 2.3.2.15), a
gamma-glutamylcysteine (gamma-EC)  transpeptidase. PC synthesis is proposed to
have two  distinct  steps:  (Step1) formation of gamma-EC concomitant with the
cleavage of  Gly  from  GSH;  and (Step 2) transfer of the gamma-EC unit to an
acceptor GSH  molecule  or  an  oligomeric  PC  peptide  (PCn). Eukaryotic PCS
typically has  a conserved N-terminal domain and a variable C-terminal domain,
both of  which  are cysteine-rich. The N-terminal core domain is sufficient to
confer a  PCS  activity and therefore can be referred to the catalytic domain.
Cyanobacterial PCS  contains the conserved N-terminal catalytic domain but not
the variable  C-terminal  domain found in eukaryotic PCSs. It can act as a GSH
hydrolase and weakly as a peptide ligase [1,2].

The catalytic  PCS  domain  belongs  to  the petidase family C83 of the papain
superfamily of  cysteine  proteases  [E1],  with  the  structurally  conserved
"catalytic triad"  and  oxyanion  hole  in  the active site. It has an overall
"crescent" shape  with  alpha/beta fold containing eight alpha-helices and six
beta-strands (see <PDB:2BTW>) [2].

The profile we developed covers the entire PCS domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: March 2009 / First entry.

[ 1] Tsuji N., Nishikori S., Iwabe O., Shiraki K., Miyasaka H., Takagi M.,
     Hirata K., Miyamoto K.
     "Characterization of phytochelatin synthase-like protein encoded by
     alr0975 from a prokaryote, Nostoc sp. PCC 7120."
     Biochem. Biophys. Res. Commun. 315:751-755(2004).
     PubMed=14975765; DOI=10.1016/j.bbrc.2004.01.122
[ 2] Vivares D., Arnoux P., Pignol D.
     "A papain-like enzyme at work: native and acyl-enzyme intermediate
     structures in phytochelatin synthesis."
     Proc. Natl. Acad. Sci. U.S.A. 102:18848-18853(2005).
     PubMed=16339904; DOI=10.1073/pnas.0505833102
[E1] https://www.ebi.ac.uk/merops/cgi-bin/famsum?family=C83

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