METAL-BINDING CHARACTERISTICS OF A PHYTOCHELATIN ANALOG (GLU-CYS)(2)GLY

The present studies were undertaken to explore the possibility of usin g 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 phytoc helatin analog peptide (Glu-Cys)(2) Gly to determine if a gene encodin g 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 show n to be quantitatively transferred to (Glu-Cys)(2) Gly. The Cd(II)-for m of the synthetic (Glu-Cys)(2)Gly peptide-like PCs was able to form s table 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 C d per peptide molecule. UV-visible, HPLC, and mass-spectral analyses i ndicated that one Hg(II) ion was chelated by each molecule of (gamma G lu-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 Elsevi er Science Inc.