Utilization of a synthetic peptide as a tool to study the interaction of heavy metals with the zinc finger domain of proteins critical for gene expression in the developing brain

The zinc finger motif belonging to the Cps(2)/His(2) family provides a stru ctural framework for a number of critical proteins which are essential for cellular function. To determine whether these domains are potential targets for heavy metal perturbation, we examined the interaction between various metals and a synthetic Cys,Mis, finger peptide, of the type present in the transcription factor Spl and an intact recombinant human Spl protein (rhSp1 ), Spl has a DNA-binding domain composed of three contiguous zinc finger mo tifs which requires Zn(II) for its activity, and may be modulated by other transition metals. Using spectrophotometric methods, the incorporation of Z n(II) and a variety of other divalent metals into this zinc finger peptide was monitored, and their ability to displace zinc ion was evaluated, Furthe rmore, the DNA-binding activity of these various metal-peptide complexes an d rhSp1 to their cognate DNA consensus sequence was examined electrophoreti cally, Our results suggested that group IIb metals [Zn(II), Cd(II), and Hg( II)] were able to complex with the peptide and bind the double-stranded DNA with high affinity as well as inhibiting Spl DNA-binding activity in a con centration-dependent manner. With the exception of Pb(II), non-transition-m etal-peptide mixtures with Ca(II), Ba(II), and Sn(II) neither exhibited the binding spectra typical of zinc finger motifs nor bound the DNA; they also had little effect on DNA-binding ability of rhSp1, Therefore, we postulate that heavy metals may modulate zinc finger proteins through structural alt erations of their zinc finger motifs and ultimately alter their function in terms of regulation of gene expression. (C) 2000 Academic Press.