5mbr

Quadruplex with flipped tetrad formed by a human telomeric sequence

spinqualitylabelsall models 5mbr Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 5mbr is a 1 chain structure with sequence from Homo sapiens. Full experimental information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Solution NMR Ligands: GF2 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed A human telomere sequence that folds into an intramolecular (3 + 1)-hybrid G-quadruplex was modified by the incorporation of 2'-fluoro-2'-deoxyriboguanosines (FG) into syn positions of its outer tetrad. A circular dichroism and NMR spectral analysis reveals a nearly quantitative switch of the G-tetrad polarity with concerted syn<-->anti transitions of all four G residues. These observations follow findings on a FG-substituted (3 + 1)-hybrid quadruplex with a different fold, suggesting a more general propensity of hybrid-type quadruplexes to undergo a tetrad polarity reversal. Two out of the three FG analogs in both modified quadruplexes adopt an S-type sugar pucker, challenging a sole contribution of N-type sugars in enforcing an anti glycosidic torsion angle associated with the tetrad flip. NMR restrained three-dimensional structures of the two substituted quadruplexes reveal a largely conserved overall fold but significant rearrangements of the overhang and loop nucleotides capping the flipped tetrad. Sugar pucker preferences of the FG analogs may be rationalized by different orientations of the fluorine atom and its resistance to be positioned within the narrow groove with its highly negative electrostatic potential and spine of water molecules. Tracing Effects of Fluorine Substitutions on G-Quadruplex Conformational Changes.,Dickerhoff J, Haase L, Langel W, Weisz K ACS Chem Biol. 2017 Mar 27. doi: 10.1021/acschembio.6b01096. PMID:28318229 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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