title: Evidence for a new Z-type left-handed DNA helix: properties of Z(WC)-DNA.
abstract: The structure of Z-DNA, currently accepted as a model for all left-handed DNAs, fails to provide convincing explanations for at least four well established properties of left-handed DNA polymers in solution. However, the major discrepancies between theory and experiment are resolved by the structure presently proposed for Z[WC]-DNA, a new left-handed, zig-zag double helix with Watson-Crick-type backbone directions. Structural features of Z[WC]-DNA include the presence of an additional H-bond between each guanine N2-amino group and an adjacent phosphate oxygen, the capacity to form four-stranded, base-matched complexes that should readily precipitate from solution, and backbone progressions that are the same as B-DNA (opposite to Z-DNA). However, since Z[WC]-DNA and Z-DNA have many parameters in common, they could be difficult to distinguish in a majority of existing experiments. In view of the close relationship of the new helix to B-DNA, which allows a relatively unhindered right-to-left transition in handedness, Z[WC]-DNA is theorized to be the left-handed structure preferentially generated in vivo by the torque available in naturally occurring DNA supercoils.
authors.affiliation: Genetics Center, Graduate School of Biomedical Sciences, University of Texas Health Science Center, Houston 77225.
authors.forename: A T
authors.initials: AT
authors.lastname: Ansevin
authors.forename: A H
authors.initials: AH
authors.lastname: Wang
mesh_terms: D001482:Base Composition; D004247:DNA / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009690:Nucleic Acid Conformation
chemical_list: D004247:DNA