title: Characterization of the selenotrisulfide formed by reaction of selenite with end-capped phytochelatin-2.
abstract: The phytochelatins are a family of peptides synthesized by plants in response to exposure to heavy metals and metalloids, including selenium in the form of selenite. The amino acid sequence of the phytochelatin (PC) peptides is (gamma-Glu-Cys)n-Gly, where n typically ranges from 2 to 5. In this paper, the products of the reaction of selenite with an end-capped analogue of PC2, Ac-(gamma-Glu-Cys)2-Gly-NH2, are characterized. Selenite reacts with Ac-(gamma-Glu-Cys)2-Gly-NH2 (Ac-PC2-NH2) to form a compound that contains an intramolecular selenotrisulfide (-SSeS-)-linkage (Se[Ac-PC2-NH2]) and oxidized Ac-PC2-NH2. Both Se[Ac-PC2-NH2] and oxidized Ac-PC2-NH2 were isolated by HPLC and were characterized by MALDI-TOF mass spectrometry, by two-dimensional 1H and 13C NMR and, in the case of Se[Ac-PC2-NH2], by 77Se NMR. Using dihedral angles determined from vicinal 1H-1H coupling constants as constraints for the conformations around the Cys(CalphaH)-Cys(CbetaH) bonds, structures were predicted for the most abundant form of both compounds by Monte Carlo molecular mechanics simulations.
authors.affiliation: Department of Chemistry, University of California, Riverside, CA 92521, USA.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Spain
authors.forename: Dallas L
authors.initials: DL
authors.lastname: Rabenstein
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D002614:Chelating Agents / Q000138:chemical synthesis / Q000737:chemistry; D005978:Glutathione; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008667:Metalloproteins / Q000138:chemical synthesis / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D054811:Phytochelatins; D012643:Selenium / Q000737:chemistry; D018036:Selenium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D018038:Sodium Selenite / Q000737:chemistry*; D013440:Sulfides / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D000596:Amino Acids; D002614:Chelating Agents; D008024:Ligands; D008667:Metalloproteins; D010455:Peptides; D018036:Selenium Compounds; D013440:Sulfides; C059755:selenotrisulfide; D054811:Phytochelatins; D005978:Glutathione; D012643:Selenium; D018038:Sodium Selenite