INTERACTION BETWEEN DNA AND A SYNTHETIC ZINC-BINDING PEPTIDE

A 23-membered peptide corresponding to a part of the DNA-binding domain of yeast transcription activator GAL-4 was synthesized and tested for interaction with zinc ions and DNA. Zinc ions altered the shape of the peptide fluorescence and CD spectra. The peptide and Zn ions formed a complex with a 1:1 stoichiometry and binding constant of(1-2).10(6) M(-1). As shown by gel filtration on a TSK column, the peptide at 10(-4)-10(-6) M exists predominantly as a dimer; the dimerization constants without and with Zn ions are 5.10(6) and 1.7.10(7) M(-1), respectively. The peptide binds to DNA, with saturation at one peptide molecule per 5 bp. The shape of the fluorimetric curves for DNA titration with the peptide indicates that the latter can bind to DNA both in monomeric and in self-associated forms (dimer or tetramer). A decrease of the peptide/DNA ratio favors the prevalence of monomeric species.