Specific interaction with guanine residues of Z-form DNA by bleomycin-nickel (III) complex

摘要

The Ni(IlI) complex of bleomycin (BLM) reacts with guanine residues of the oligomer duplex only under high salt condition (4.5 M NaCl) where the (tlC-dG),, sequence exists as the isolated Z-form segment. In addition, the (dC-dG)n inserts were subcloned into a plasmid so that reactivity of the BLM-Ni(IIl) complex with restriction fragments could be examined. Results are reported for two fragments: an EcoRl-Ddel fragment in which the (dC-ilG),, insert is Hanked at the 5' end by a segment of B-DNA and a Hindlll-Ddel fragment in which the UlC-dG)n fragment is embedded at both ends by stable B-DNA forming segments. The BLM-Ni(III) complex does not bind to (dC-dG)s sequence of pBRZIO DNA fragment under any conditions, but to several guanine residues of (dC-dG)8 and (dC-dG)l2 sequences of pBRZIfi and pBRZ24 DNA fragments in 4.5 M NaCl solution. In the fragments of pBRZ16 and pBRZ24 DNAs, the BLM-Ni(M) complex reacts with most of guanine bases of (dC-dG)^ and (dC-dG)12.