title: Structure of d(TGCGCG).d(CGCGCA) in two crystal forms: effect of sequence and crystal packing in Z-DNA.
abstract: The sequence d(TGCGCG).d(CGCGCA) crystallized in two crystal forms, orthorhombic and hexagonal, in the presence of cobalt hexammine chloride, a known inducer of the left-handed Z-form of DNA. The crystal structures have been solved and refined at 1.71 A resolution in space group P2(1)2(1)2(1) and 2.0 A resolution in space group P6(5). The orthorhombic structure contains one Z-DNA hexamer duplex, while the hexagonal structure contains two hexamer duplexes in the structure. Of the latter, one is situated on a crystallographic sixfold screw axis, leading to disorder. This paper reports the effects of sequence and crystal packing on the structure of Z-type DNA. The structures lend additional support to the authors' earlier conclusion that a stretch of four C.G base pairs is sufficient to nucleate and define the regular model of the left-handed helix based on the structure of d(CGCGCG)2.
authors.affiliation: Department of Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai 600 025, India.
authors.forename: S
authors.initials: S
authors.lastname: Thiyagarajan
authors.forename: S S
authors.initials: SS
authors.lastname: Rajan
authors.forename: N
authors.initials: N
authors.lastname: Gautham
mesh_terms: D020029:Base Pairing; D001483:Base Sequence; D018360:Crystallography, X-Ray; D043542:DNA, Z-Form / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D043542:DNA, Z-Form; D009838:Oligodeoxyribonucleotides; D014867:Water