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AvtorZavasnik, Jaka
Podbevšek, Peter
Plavec, Janez
Naslov Observation of water molecules within the bimolecular d(G [sub] 3CT [sub] 4G [sub] 3C) [sub] 2 G-quadruplex / Jaka Zavasnik, Peter Podbevšek and Janez Plavec
Vrsta/vsebinatype of material članek - sestavni del
Fizični opisstr. 4155-4161
Predmetne oznake (nekontrolirane)oligonucleotides / G-quadruplexes / water molecules
PovzetekG-Rich oligonucleotides with cytosine residues in their sequences can form G-quadruplexes where G-quartets are flanked by G C Watson-Crick base pairs. Inan attempt to probe the role of cations in stabilization of a structural element with two G C base pairs stacked on a G-quartet, we utilized solution state nuclear magnetic resonance to study the folding of the d(G3CT4G3C) oligonucleotide into a G-quadruplex upon addition of 15NH4+ ions. Its bimolecular structure exhibits antiparallel strands with edge-type loops. Two G-quartets in the core of the structure are flanked by a couple of Watson-Crick G C base pairs in a sheared arrangement. The topology is equivalent to the solution state structure of the same oligonucleotide in the presence of Na+ and K+ ions [Kettani, A., et al. (1998) J. Mol. Biol.282, 619,and Bouaziz, S., et al. (1998) J. Mol. Biol.282, 637). A single ammonium ion binding site was identified between adjacent G-quartets, but three sites were expected. The remaining potential cation binding sites between G-quartetsand G C base pairs are occupied by water molecules. This is the first observation of long-lived water molecules within a G-quadruplex structure. The flanking G C base pairs adopt a coplanar arrangement and apparently do not require cations to neutralize unfavorable electrostatic interactions among proximal carbonyl groups. A relatively fast movement of ammonium ions from the inner binding site to bulk with the rate constants of 21 s-1 was attributed to the lack of hydrogen bonds between adjacent G C base pairs and the flexibility of the T4 loops.
Glej publikacijo TI=Biochemistry ISSN: 0006-2960.- Vol. 50, no. 19 (2011), str. 4155-4161