SPECIFIC INTERACTION WITH GUANINE RESIDUES OF Z-FORM DNA BY BLEOMYCIN-NICKEL(III) COMPLEX

The Ni(III) complex of bleomycin (BLM) reacts with guanine residues of the oligomer duplex only under high salt condition (4.5 M NaCl) where the (dC-dG)(6) sequence exists as the isolated Z-form segment. In add ition, the (dC-dG)(n) inserts were subcloned into a plasmid so that re activity of the BLM-Ni(III) complex with restriction fragments could b e examined. Results are reported for two fragments: an EcoRI-DdeI frag ment in which the (dC-dG)(n) insert is flanked at the 5' end by a segm ent of B-DNA and a HindIII-DdeI fragment in which the (dC-dG)(n) fragm ent is embedded at both ends by stable B-DNA forming segments. The BLM -Ni(III) complex does not bind to (dC-dG)(5) sequence of pBRZ10 DNA fr agment under any conditions, but to several guanine residues of (dC-dG )(8) and (dC-dG)(12) sequences of pBRZ16 and pBRZ24 DNA fragments in 4 .5 M NaCl solution. In the fragments of pBRZ16 and pBRZ24 DNAs, the BL M-Ni(III) complex reacts with most of guanine bases of (dC-dG)(8) and (dC-dG)(12).