SPECTROSCOPIC CHARACTERIZATION OF A DNA-BINDING DOMAIN, Z-ALPHA FROM THE EDITING ENZYME, DSRNA ADENOSINE-DEAMINASE - EVIDENCE FOR LEFT-HANDED Z-DNA IN THE Z-ALPHA-DNA COMPLEX

Double-stranded RNA adenosine deaminase (ADAR1) is an ubiquitous enzym e in metazoa that edits pre-mRNA changing adenosine to inosine in regi ons of double-stranded RNA. Z alpha, an N-terminal domain of human ADA R1 encompassing 76 amino acid residues, shows apparent specificity for the left-handed Z-DNA conformation adopted by alternating (dGdC) poly mers modified by bromination or methylation, as well as for (dGdC)(13) inserts present in supercoiled plasmids. Here, a combination of circu lar dichroism, fluorescence, and gel-retardation studies is utilized t o characterize recombinant Z alpha peptide and to examine its interact ion with DNA. Results from laser-Raman spectroscopy experiments provid e direct evidence for the existence of Z-DNA in peptide-DNA complexes.