AtPCS1, a phytochelatin synthase from Arabidopsis: isolation and in vitro reconstitution.
Phytochelatins, a class of posttranslationally synthesized peptides, play a pivotal role in heavy metal, primarily Cd2+, tolerance in plants and fungi by chelating these substances and decreasing their free concentrations. Derived from glutathione and related thiols by the action of gamma-glutamylcysteine dipeptidyl transpeptidases (phytochelatin synthases; EC 2.3.2.15), phytochelatins consist of repeating units of gamma-glutamylcysteine followed by a C-terminal Gly, Ser, or beta-Ala residue [poly-(gamma-Glu-Cys)n-Xaa]. Here we report the suppression cloning of a cDNA (AtPCS1) from Arabidopsis thaliana encoding a 55-kDa soluble protein that enhances heavy-metal tolerance and elicits Cd2+-activated phytochelatin accumulation when expressed in Saccharomyces cerevisiae. On the basis of these properties and the sufficiency of immunoaffinity-purified epitope-tagged AtPCS1 polypeptide for high rates of Cd2+-activated phytochelatin synthesis from glutathione in vitro, AtPCS1 is concluded to encode the enzyme phytochelatin synthase.
Vatamaniuk
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Plant Science Institute, Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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D000595:Amino Acid Sequence; D019881:Aminoacyltransferases / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D016415:Sequence Alignment
D010940:Plant Proteins; D019881:Aminoacyltransferases; C093784:glutathione gamma-glutamylcysteinyltransferase