title: Crystal structure of an oligonucleotide duplex containing G.G base pairs: influence of mispairing on DNA backbone conformation.
abstract: The structure of the G.G mispaired dodecanucleotide d(CGCGAATTGGCG)2 has been solved by x-ray crystallography and refined to an R factor of 18.8% at 2.2 A resolution for 3513 reflections. The dodecamer crystallizes as a B-type DNA double helix. It contains two G(anti).G(syn) base pairs--i.e., G-4/G-16(anti).G-21/G-9(syn). The Hoogsteen base pairing involves atoms O-6 and N-7 of the guanine in the syn conformation with atoms N-1 and N-2 of the anti-paired purine. One G.G base pair has a bifurcated hydrogen bond between G-4(N-1)...G-21(N-7) and G-4(N-1)...G-21(O-6). There is little overall structural distortion of the double helix induced as a consequence of the mispairing. The helical width is significantly increased by comparison with the structure of the native duplex, and the minor groove width in the 5'-AATT region is decreased. The G.G base pairing induces high-BII phosphate conformations at residues G-9 and T-20 in addition to more normal BII conformations at G-10 and G-22. It is suggested that these backbone aberrations provide signals for the facile repairability of G.G mispairs in DNA.
authors.affiliation: Cancer Research Campaign Biomolecular Structure Unit, Institute of Cancer Research, Sutton, Surrey, United Kingdom.
authors.forename: J V
authors.initials: JV
authors.lastname: Skelly
authors.forename: K J
authors.initials: KJ
authors.lastname: Edwards
authors.forename: T C
authors.initials: TC
authors.lastname: Jenkins
authors.forename: S
authors.initials: S
authors.lastname: Neidle
mesh_terms: D001482:Base Composition; D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D009838:Oligodeoxyribonucleotides; D004247:DNA