1a8w
A K+ CATION-INDUCED CONFORMATIONAL SWITCH WITHIN A LOOP SPANNING SEGMENT OF A DNA QUADRUPLEX CONTAINING G-G-G-C REPEATS, NMR, 8 STRUCTURES
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OverviewOverview
We have identified a unique structural transition (in slow exchange on the, NMR time scale) in the tertiary fold of the d(G-G-G-C-T4-G-G-G-C), quadruplex on proceeding from Na+ to K+ as counterion in aqueous solution., Both monovalent cation-dependent conformations exhibit certain common, structural features, which include head-to-tail dimerization of two, symmetry-related stem-hairpin loops, adjacent strands which are, antiparallel to each other and adjacent stacked G(syn).G(anti)., G(syn).G(anti) tetrads in the central core of the quadruplexes. The Na and, K cation stabilized structures of the d(G-G-G-C-T4-G-G-G-C) quadruplexes, differ in the conformations of the T-T-T-T loops, the relative alignment, of G.C base-pairs positioned opposite each other through their major, groove edges and potentially in the number of monovalent cation binding, sites. We have identified potential K cation binding cavities within the, symmetry-related T-T-T-G segments, suggesting the potential for two, additional monovalent cation binding sites in the K cation-stabilized, quadruplex relative to its Na cation-stabilized counterpart. Modeling, studies suggest that the major groove edges of guanine residues in, Watson-Crick G.C base-pairs could potentially be bridged by coordinated K, cations in the d(G-G-G-C-T4-G-G-G-C) quadruplex in KCl solution in, contrast to formation of G.C.G.C tetrads for the corresponding quadruplex, in NaCl solution. Our results defining the molecular basis of a Na to K, cation-dependent conformational switch in the loop spanning segment of the, d(G-G-G-C-T4-G-G-G-C) quadruplex may have relevance to recent observations, that specific K cation coordinated loop conformations within quadruplexes, exhibit inhibitory activity against HIV integrase.
About this StructureAbout this Structure
1A8W is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
ReferenceReference
A K cation-induced conformational switch within a loop spanning segment of a DNA quadruplex containing G-G-G-C repeats., Bouaziz S, Kettani A, Patel DJ, J Mol Biol. 1998 Sep 25;282(3):637-52. PMID:9737927
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