186d
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SOLUTION STRUCTURE OF THE TETRAHYMENA TELOMERIC REPEAT D(T2G4)4 G-TETRAPLEX
OverviewOverview
BACKGROUND: Telomeres in eukaryotic organisms are protein-DNA complexes, which are essential for the protection and replication of chromosomal, termini. The telomeric DNA of Tetrahymena consists of T2G4 repeats, and, models have been previously proposed for the intramolecular folded, structure of the d(T2G4)4 sequence based on chemical footprinting and, cross-linking data. A high-resolution solution structure of this sequence, would allow comparison with the structures of related G-tetraplexes., RESULTS: The solution structure of the Na(+)-stabilized d(T2G4)4 sequence, has been determined using a combined NMR-molecular dynamics approach. The, sequence folds intramolecularly into a right-handed G-tetraplex containing, three stacked G-tetrads connected by linker segments consisting of a, G-T-T-G lateral loop, a central T-T-G lateral loop and a T-T segment that, spans the groove through a double chain reversal. The latter T-T, connectivity aligns adjacent G-G-G segments in parallel and introduces a, new G-tetraplex folding topology with unprecedented combinations of strand, directionalities and groove widths, as well as guanine syn/anti, distributions along individual strands and around individual G-tetrads., CONCLUSIONS: The four repeat Tetrahymena and human G-tetraplexes, which, differ by a single guanine for adenine substitution, exhibit strikingly, different folding topologies. The observed structural polymorphism, establishes that G-tetraplexes can adopt topologies which project, distinctly different groove dimensions, G-tetrad base edges and linker, segments for recognition by, and interactions with, other nucleic acids, and proteins.
About this StructureAbout this Structure
186D is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
ReferenceReference
Solution structure of the Tetrahymena telomeric repeat d(T2G4)4 G-tetraplex., Wang Y, Patel DJ, Structure. 1994 Dec 15;2(12):1141-56. PMID:7704525
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