Classical Cys₂His₂ zinc finger peptides are rapidly oxidized by either H₂O₂ or O₂ irrespective of metal coordination

ZIF268, a member of the classical zinc finger protein family, contains three Cys₂His₂ zinc binding domains that together recognize the DNA sequence 5′-AGCGTGGGCGT-3′. These domains can be fused to an endonuclease to make a chimeric protein to target and cleave specific DNA sequences. A peptide corresponding to these domains, named ZIF268-3D, has been prepared to determine if the zinc finger domain itself can promote DNA cleavage when a redox active metal ion, Fe(II), is coordinated. The UV-vis absorption spectrum of Fe(II)-ZIF268-3D is indicative of Fe(II) coordination. Using fluorescence anisotropy, we demonstrate that Fe(II)-ZIF268-3D binds selectively to its target DNA in the same manner as Zn(II)-ZIF268-3D. In the presence of added oxidant, H₂O₂ or O₂, DNA cleavage is not observed by Fe(II)-ZIF268-3D. Instead, the peptide itself is rapidly oxidized. Similarly, Zn(II)-ZIF268-3D and apo-ZIF268-3D are rapidly oxidized by H₂O₂ or O ₂, and we propose that ZIF268-3D is highly susceptible to oxidation.