149d

SOLUTION STRUCTURE OF A PYRIMIDINE(DOT)PURINE(DOT) PYRIMIDINE DNA TRIPLEX CONTAINING T(DOT)AT, C+(DOT)GC AND G(DOT)TA TRIPLES

spinqualitylabelsall models 149d, 14 NMR models Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 149d is a 3 chain structure. Full experimental information is available from OCA. For a guided tour on the structure components use FirstGlance. Resources: FirstGlance, OCA, RCSB, PDBsum Publication Abstract from PubMed BACKGROUND: Under certain conditions, homopyrimidine oligonucleotides can bind to complementary homopurine sequences in homopurine-homopyrimidine segments of duplex DNA to form triple helical structures. Besides having biological implications in vivo, this property has been exploited in molecular biology applications. This approach is limited by a lack of knowledge about the recognition by the third strand of pyrimidine residues in Watson-Crick base pairs. RESULTS: We have therefore determined the solution structure of a pyrimidine.purine.pyrimidine (Y.RY) DNA triple helix containing a guanine residue in the third strand which was postulated to specifically recognize a thymine residue in a Watson-Crick TA base pair. The structure was solved by combining NMR-derived restraints with molecular dynamics simulations conducted in the presence of explicit solvent and counter ions. The guanine of the G-TA triple is tilted out of the plane of its target TA base pair towards the 3'-direction, to avoid a steric clash with the thymine methyl group. This allows the guanine amino protons to participate in hydrogen bonds with separate carbonyls, forming one strong bond within the G-TA triple and a weak bond to an adjacent T.AT triple. Dramatic variations in helical twist around the guanine residue lead to a novel stacking interaction. At the global level, the Y.RY DNA triplex shares several structural features with the recently solved solution structure of the R.RY DNA triplex. CONCLUSIONS: The formation of a G.TA triple within an otherwise pyrimidine.purine.pyrimidine DNA triplex causes conformational realignments in and around the G.TA triple. These highlight new aspects of molecular recognition that could be useful in triplex-based approaches to inhibition of gene expression and site-specific cleavage of genomic DNA. Solution structure of a pyrimidine.purine.pyrimidine DNA triplex containing T.AT, C+.GC and G.TA triples.,Radhakrishnan I, Patel DJ Structure. 1994 Jan 15;2(1):17-32. PMID:8075980 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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