Metal Ion Binding to a Zinc Finger Peptide Containing the Cys-X2-Cys-X4-His-X4-Cys Domain of a Nucleic Acid Binding Protein Encoded by theDrosophilaFw-Element

The metal binding properties of a 18-residue zinc finger peptide containing a CCHC box which reproduces one of the cysteine-rich domains of a putative nucleic acid binding protein encoded by the Fw transposable element fromDrosophila melanogasterwere investigated through electronic and1H NMR spectroscopy. Dissociation constants of 2(±1)×10−12M and 4(±1)×10−7M were determined for the Zn2+and Co2+adduct, respectively. These values are similar to those for other CCHC-peptides investigated previously, although the length of the spacer between the second cysteine and the histidine apparently exerts some influence on the spectral properties and on the stability of the Co2+-peptide adduct. The1H NMR spectrum of the present Co2+-derivative contains a number of well resolved hyperfine-shifted resonances between 350 and −50 ppm which arise from the metal binding residues and nearby groups. These peaks can in principle be profitably exploited to monitor protein-nucleic acid interactions.