Crystallization and characterization of the thallium form of the Oxytricha nova G-quadruplex

Nucleic Acids Res. 2006;34(16):4506-14. doi: 10.1093/nar/gkl616. Epub 2006 Aug 31.


The crystal structure of the Tl+ form of the G-quadruplex formed from the Oxytricha nova telomere sequence, d(G4T4G4), has been solved to 1.55 A. This G-quadruplex contains five Tl+ ions, three of which are interspersed between adjacent G-quartet planes and one in each of the two thymine loops. The structure displays a high degree of similarity to the K+ crystal structure [Haider et al. (2002), J. Mol. Biol., 320, 189-200], including the number and location of the monovalent cation binding sites. The highly isomorphic nature of the two structures, which contain such a large number of monovalent binding sites (relative to nucleic acid content), verifies the ability of Tl+ to mimic K+ in nucleic acids. Information from this report confirms and extends the assignment of 205Tl resonances from a previous report [Gill et al. (2005), J. Am. Chem. Soc., 127, 16 723-16 732] where 205Tl NMR was used to study monovalent cation binding to this G-quadruplex. The assignment of these resonances provides evidence for the occurrence of conformational dynamics in the thymine loop region that is in slow exchange on the 205Tl timescale.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Binding Sites
  • Cations, Monovalent / chemistry
  • Crystallography, X-Ray
  • DNA / chemistry*
  • DNA, Protozoan / chemistry*
  • G-Quadruplexes
  • Guanine / chemistry*
  • Hydrogen Bonding
  • Isotopes
  • Models, Molecular
  • Nuclear Magnetic Resonance, Biomolecular
  • Nucleic Acid Conformation
  • Oxytricha / genetics*
  • Telomere / chemistry*
  • Thallium / chemistry
  • Water / chemistry


  • Cations, Monovalent
  • DNA, Protozoan
  • Isotopes
  • Water
  • Guanine
  • DNA
  • Thallium