Z* DNA, the left-handed helical form of poly[d(G-C)] in MgCl2-ethanol, is biologically active.

摘要: Abstract The interconversion between the right (R) and left (L) helical forms of poly[d(G-C)] occurs at low concentrations MgCl2 EtOH, acting together in a highly synergistic manner. Thus, cooperative R---L transition is induced by only 0.4 mM 4 MM combination with 20% 10% respectively. The L form formed under these conditions has spectroscopic properties (absorption, circular dichroism) previously demonstrated high salt (Pohl Jovin, 1972) thought to correspond left-handed Z DNA structures recently established X-ray crystallography (Wang et al., 1979; Drew 1980). However, Mg2+-EtOH (which we designate as Z* DNA) unique properties: a) it can be sedimented readily out solution speed, indicative condensation intermolecular aggregation; b) supports binding several intercalating (ethidium bromide, actinomycin D) non-intercalating (mithramycin) drugs, although interact preferentially R (i.e., B) DNA; c) functions template for Escherichia coli RNA polymerase. B DNAs generated identical ionic compared number biochemical systems. Our results suggest that may physiological serve biological function.