title: Chelation of cadmium ions by phytochelatin synthase: role of the cysteine-rich C-terminal.
abstract: The interactions between Cd(2+) and the C-terminal region of phytochelatin (PC) synthase using recombinant wild-type and mutant PC synthase were studied. We show that site-directed mutagenesis of Cys residues at C(358)C(359)XXXC(363)XXC(366) motif decreases the number of Cd(2+) and other heavy metal ions interacting with the enzyme, and that the motif binds the metals discriminatingly. The optimum binding ratio of PC synthase to Cd(2+) was also determined. The findings indicate that Cys exists as a free SH residue and that it is involved in the regulation of PC enzyme activity by transferring the metals into closer proximity with the catalytic domain. These results are important in understanding heavy metal detoxification mechanisms in higher plants, a step towards phytoremediated-applications.
authors.affiliation: School of Materials Science, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, Japan.
authors.forename: Mun'delanji
authors.initials: M
authors.lastname: Vestergaard
authors.forename: Sachiko
authors.initials: S
authors.lastname: Matsumoto
authors.forename: Shingo
authors.initials: S
authors.lastname: Nishikori
authors.forename: Kentaro
authors.initials: K
authors.lastname: Shiraki
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Hirata
authors.forename: Masahiro
authors.initials: M
authors.lastname: Takagi
mesh_terms: D019881:Aminoacyltransferases / Q000737:chemistry*; D001665:Binding Sites; D002104:Cadmium / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry*; D004789:Enzyme Activation; D007477:Ions / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry
chemical_list: D007477:Ions; D011994:Recombinant Proteins; D002104:Cadmium; D019881:Aminoacyltransferases; C093784:glutathione gamma-glutamylcysteinyltransferase; D003545:Cysteine