Solution structure of the Oxytricha telomeric repeat d[G4(T4G4)3] G-tetraplex

J Mol Biol. 1995 Aug 4;251(1):76-94. doi: 10.1006/jmbi.1995.0417.


The solution structure of Oxytricha telomere sequence d[G4(T4G4)3] in 0.1 M Na+ containing solution has been determined using a combined NMR-molecular dynamics approach including relaxation matrix refinement. This four G4 repeat sequence folds intramolecularly into a right-handed G-tetraplex containing four stacked G-tetrads which are connected by two lateral T4 loops and a central diagonal T4 loop. The guanine glycosidic bonds adopt a syn-anti alternation along the full length of the d[G4(T4G4)3] sequence while the orientation around adjacent G-tetrads switches between syn.syn.anti.anti and anti.anti.syn.syn alignments. Four distinct grooves are formed by the parallel (two of medium width) and anti-parallel (one wide and one narrow width) alignment of adjacent G-G-G-G segments in the G-tetraplex. The T4 residues in the diagonal loop are well-defined while the T4 residues in both lateral loops are under-defined and sample multiple conformations. The solution structure of the Na(+)-stabilized Oxytricha d[G4(T4G4)3] G-tetraplex and an earlier solution structure reported from our laboratory on the Na(+)-stabilized human d[AG3(T2AG3)3] G-tetraplex exhibit a common folding topology defined by the same syn/anti distribution of guanine residues along individual strands and around individual G-tetrads, as well as a common central diagonal loop which defines the strand directionalities. The well-resolved proton NMR spectra associated with the d[G4(T4G4)3] G-tetraplex opens the opportunity for studies ranging from cation-dependent characterization of G-tetraplex conformation and hydration to ligand and protein recognition of the distinct grooves associated with this folding topology.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • DNA / chemistry*
  • Guanine / chemistry
  • Inosine / chemistry
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Molecular Sequence Data
  • Nucleic Acid Conformation*
  • Oxytricha / chemistry*
  • Oxytricha / genetics
  • Protons
  • Repetitive Sequences, Nucleic Acid*
  • Sodium / chemistry
  • Solutions
  • Telomere / chemistry*


  • Protons
  • Solutions
  • Inosine
  • Guanine
  • DNA
  • Sodium

Associated data

  • PDB/201D