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 O2, and we propose that ZIF268-3D is highly susceptible to oxidation.