Spectroscopic Characterization of a DNA-Binding Domain, Zα, from the Editing Enzyme, dsRNA Adenosine Deaminase:  Evidence for Left-Handed Z-DNA in the Zα−DNA Complex

Double-stranded RNA adenosine deaminase (ADAR1) is an ubiquitous enzyme in metazoa that edits pre-mRNA changing adenosine to inosine in regions of double-stranded RNA. Zα, an N-terminal domain of human ADAR1 encompassing 76 amino acid residues, shows apparent specificity for the left-handed Z-DNA conformation adopted by alternating (dGdC) polymers modified by bromination or methylation, as well as for (dGdC)13 inserts present in supercoiled plasmids. Here, a combination of circular dichroism, fluorescence, and gel-retardation studies is utilized to characterize recombinant Zα peptide and to examine its interaction with DNA. Results from laser-Raman spectroscopy experiments provide direct evidence for the existence of Z-DNA in peptide−DNA complexes.