Spectroscopic characterization of metal bound phytochelatin analogue (Glu-Cys)4-Gly.
The metal ion binding properties of a phytochelatin (PC) analogue, (Glu-Cys)4-Gly (named as EC4), have been studied by a divalent metal ion binding assay monitored by UV-visible spectroscopy, circular dichroism and NMR spectroscopy. Spectro- photometric titration with different divalent metal ions have revealed that the stiochoimetry of metal-bound EC4 was 1:1, and its metal binding affinities with different divalent metal ions in the order of Cd(II)>Cu(II)>Zn(II)>Pb(II)>Ni(II)>Co(II). UV-visible spectroscopic analysis of metal complexes indicated that four sulfur atoms in cysteine residues are attributable to ligand-to-metal charge transfer (LMCT) between divalent metal ions and EC4, and further confirmed by 1D H1 NMR study and Circular Dichroism. In addition, Circular Dichroism spectra of both free and metal-bound forms of EC4 revealed that metal coordination drives the nonapeptide chain to fold into a turned conformation. The comprehensive analysis of spectroscopic properties of the nonapeptide complexed with metal ions not only provides a fundamental description of the metal ion binding properties of PC analogue, but also shows a correlation between metal binding affinity of PC analogue and the induction activity of metal ions.
Cheng
Yongsheng
Y
Laboratory of Molecular Biology and MOE Laboratory of Protein Science, Department of Biological Science and Biotechnology, Tsinghua University, Beijing 100084, China.
Yan
Yong-Bin
YB
Liu
Jinyuan
J
D000596:Amino Acids / Q000737:chemistry; D005978:Glutathione / Q000138:chemical synthesis / Q000737:chemistry*; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D019216:Metals, Heavy / Q000737:chemistry*; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D054811:Phytochelatins
D000596:Amino Acids; D007477:Ions; D019216:Metals, Heavy; D009842:Oligopeptides; C505740:glutamyl-cysteinyl-glutamyl-cysteinyl-glutamyl-cysteinyl-glutamyl-cysteinyl-glycine; D054811:Phytochelatins; D005978:Glutathione