CHICKEN DOUBLE-STRANDED-RNA ADENOSINE-DEAMINASE HAS APPARENT SPECIFICITY FOR Z-DNA

A M(r) 140,000 protein has been purified from chicken lungs to apparen t homogeneity. The protein binds with high affinity to a non-BNA confo rmation, which is most likely to be Z-DNA. The protein also has a bind ing site for double-stranded RNA (dsRNA). Peptide sequences from this protein show similarity to dsRNA adenosine deaminase, an enzyme that d eaminates adenosine in dsRNA to form inosine. Assays for this enzyme c onfirm that dsRNA adenosine deaminase activity and Z-DNA binding are p roperties of the same molecule. The coupling of these two activities i n a single molecule may indicate a distinctive mechanism of gene regul ation that is, in part, dependent on DNA topology. As such, DNA topolo gy, through its effects on the efficiency and extent of RNA editing ma y be important in the generation of new phenotypes during evolution.