Tracing Effects of Fluorine Substitutions on G-Quadruplex Conformational Changes.
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 aFG-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 threeFG 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 theFG 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.
Institute of Biochemistry, Ernst-Moritz-Arndt University Greifswald , Felix-Hausdorff-Str. 4, D-17487 Greifswald, Germany.
Jonathan
J
Dickerhoff
Institute of Biochemistry, Ernst-Moritz-Arndt University Greifswald , Felix-Hausdorff-Str. 4, D-17487 Greifswald, Germany.
Linn
L
Haase
Institute of Biochemistry, Ernst-Moritz-Arndt University Greifswald , Felix-Hausdorff-Str. 4, D-17487 Greifswald, Germany.
Walter
W
Langel
Institute of Biochemistry, Ernst-Moritz-Arndt University Greifswald , Felix-Hausdorff-Str. 4, D-17487 Greifswald, Germany.
Klaus
0000-0002-2736-6606
K
Weisz
D003849:Deoxyguanosine / Q000737:chemistry; D005461:Fluorine / Q000737:chemistry*; D054856:G-Quadruplexes; D006801:Humans; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D016615:Telomere / Q000235:genetics
D005461:Fluorine; D003849:Deoxyguanosine