ENANTIOSPECIFIC RECOGNITION OF DNA BY BLEOMYCIN

The specific double-stranded DNA recognition mechanism of bleomycin was investigated using L-d(CGCGCG), the enantiomer of natural D-d(CGCGCG). The L-enantiomer was clearly shown not to be cleaved at all by bleomycin under the same conditions that the corresponding D-enantiomer was cleaved, but the conventional DNA-binding domain of bleomycin was able to bind to the L-enantiomer to essentially the same extent as the natural one, as shown by H-1 NMR titration experiments. However, other protons in the metal-binding domain and linker moiety showed different behaviors depending on the chirality of DNA. The DNA-binding domain thus binds to DNA with a nonenantiospecific manner, and the primary determinant for specific DNA recognition of bleomycin is the linker-metal-binding region. After binding of the DNA binding domain to a right-handed B-form DNA, the remaining moiety should recognize specifically the shape of the DNA (''induced-fit''). Thus, L-oligonucleotides are a powerful tool for discriminating specific interactions from nonspecific association for DNA-drug interaction studies.