Metal-binding characteristics of a phytochelatin analog (Glu-Cys)(2)Gly

The present studies were undertaken to explore the possibility of using synthetically designed genes encoding phytochelatin analog (Glu-Cys)(n) Gly peptides in transgenic plants for phytoremediation. We studied the metalchelating characteristics of a synthetically prepared phytochelatin analog peptide (Glu-Cys)(2) Gly to determine if a gene encoding such a peptide might be useful in phytoremediation, as a first step. Studies with Cd(II), Hg(II), and Pb(II) show that the synthetic (Glu-Cys)(2) Gly peptide exhibits metal-chelating properties similar to the phytochelatin (gamma Glu-Cys)(2) Gly. GSH-bound metals were also shown to be quantitatively transferred to (Glu-Cys)(2) Gly. The Cd(II)-form of the synthetic (Glu-Cys)(2)Gly peptide-like PCs was able to form stable complexes with sulfide. The spectroscopic properties of (Glu-Cys)(2) Gly-coated complexes of CdS were comparable to those exhibited by (gamma Glu-Cys)(2) Gly-coated CdS particles. Both (gamma Glu-Cys)(2) Gly and (Glu-Cys)(2) Gly exhibited a Cd-binding stoichiometry of 0.5 Cd per peptide molecule. UV-visible, HPLC, and mass-spectral analyses indicated that one Hg(II) ion was chelated by each molecule of (gamma Glu-Cys)(2) Gly or (Glu-Cys)(2) Gly. Each molecule of (gamma Glu-Cys)(2) Gly or (Glu-Cys)(2) Gly bound to one atom of Pb(II). (C) 1997 Elsevier Science Inc.