Isolation of Z-DNA-containing plasmids.

A purified, monoclonal antibody, specific for the left-handed Z-form of poly(dG-dC), was coupled covalently to Sephacryl S-1000 beads. Such an antibody column provides a convenient method to isolate and purify those plasmid DNAs that contain Z-DNA from a large excess of other DNAs, RNA, etc. From a library of Escherichia coli DNA, cloned into the vector plasmid pUC-8, several recombinant plasmids were isolated, which bind to this antibody. Thus, E. coli contains sequences, which in "natural" negatively supercoiled DNA, adopt a left-handed Z-DNA-like conformation.