title: Structure of a d(TGGGGT) quadruplex crystallized in the presence of Li+ ions.
abstract: A parallel 5'-d(TGGGGT)-3' quadruplex was formed in Na(+) solution and crystallized using lithium sulfate as the main precipitating agent. The X-ray structure was determined to 1.5 A resolution in space group P2(1) by molecular replacement. The asymmetric unit consists of a characteristic motif of two quadruplexes stacked at their 5' ends. All nucleotides are clearly defined in the density and could be positioned. A single bound Li(+) ion is observed at the surface of the column formed by the two joined molecules. Thus, this small alkali metal ion appears to be unsuitable as a replacement for the Na(+) ion in the central channel of G-quartets, unlike K(+) or Tl(+) ions. A well conserved constellation of water molecules is observed in the grooves of the dimeric structure.
authors.affiliation: Laboratoire de BioCristallographie, Institut de Biologie et Chimie des Protéines, CNRS-UCBL, UMR 5086, IFR128 BioSciences Lyon-Gerland, 7 Passage du Vercors, 69007 Lyon, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Creze
authors.forename: Bruno
authors.initials: B
authors.lastname: Rinaldi
authors.forename: Richard
authors.initials: R
authors.lastname: Haser
authors.forename: Philippe
authors.initials: P
authors.lastname: Bouvet
authors.forename: Patrice
authors.initials: P
authors.lastname: Gouet
mesh_terms: D001483:Base Sequence; D003460:Crystallization; D018360:Crystallography, X-Ray; D003854:Deoxyribonucleotides / Q000737:chemistry* / Q000235:genetics; D008094:Lithium / Q000737:chemistry; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012964:Sodium / Q000737:chemistry; D055672:Static Electricity; D014867:Water / Q000737:chemistry
chemical_list: D003854:Deoxyribonucleotides; D014867:Water; D008094:Lithium; D012964:Sodium