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首页> 外文期刊>Journal of Molecular Biology >A K cation-induced conformational switch within a loop spanning segment of a DNA quadruplex containing G-G-G-C repeats
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A K cation-induced conformational switch within a loop spanning segment of a DNA quadruplex containing G-G-G-C repeats

机译：包含G-G-G-C重复序列的DNA四链体的环跨段内的K阳离子诱导的构象转换

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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-T-4-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-T-4-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-T-4-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-T-4-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. (C) 1998 Academic Press. [References: 37]
机译：我们已经确定了d（G-G-G-C-T-4-G-G-G-G-C）四重体在从Na +到K +的水溶液中作为抗衡离子时的三重折叠中的独特结构转变（在NMR时间尺度上缓慢交换）。两种单价阳离子依赖性构象均显示某些共同的结构特征，包括两个对称相关的茎-发夹环的头尾尾二聚化，相邻链彼此反平行以及相邻堆叠G（syn）.G（anti） .G（syn）.G（反）在四链体的中心核心四联。 d（GGGCT-4-GGGC）四链体的Na和K阳离子稳定结构的不同之处在于TTTT环的构型，通过其主要凹槽边缘彼此相对放置的GC碱基对的相对排列以及潜在的数目一价阳离子结合位点。我们已经确定了对称相关的T-T-T-G区段内潜在的K阳离子结合腔，这表明相对于其Na阳离子稳定的对应物，在K阳离子稳定的四链体中可能存在两个另外的单价阳离子结合位点。建模研究表明，Watson-Crick GC碱基对中鸟嘌呤残基的主要凹槽边缘可能由KCl溶液中d（GGGCT-4-GGGC）四元体中配位的K阳离子桥接，而不是形成GCGC四元体。 NaCl溶液中相应的四链体。我们的结果定义了d（GGGCT-4-GGGC）四链体环跨段中Na到K阳离子依赖的构象转换的分子基础，这可能与最近的观察结果有关，即四链体中特定的K阳离子配位环构象具有抑制活性对抗艾滋病毒。 （C）1998年学术出版社。 [参考：37]

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