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The RNA i-motif.

机译:RNA i-基序。

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摘要

Oligodeoxynucleotides with stretches of cytidine residues associate into a four-stranded structure, the i-motif, in which two head-to-tail, intercalated, parallel-stranded duplexes are held together by hemiprotonated C.C+ pairs. We have investigated the possibility of forming an i-motif structure with C-rich ribonucleic acids. The four C-rich RNAs studied, r(UC5), r(C5), r(C5U) and r(UC3), associate into multiple intercalated structures at acidic pH. r(UC5) forms two i-motif structures that differ by their intercalation topologies. We report on a structural study of the main form and we analyze the small conformational differences found by comparison with the DNA i-motif. The stacking topology of the main structure avoids one of the six 2'-OH/2'-OH repulsive contacts expected in a fully intercalated structure. The C3'-endo pucker of the RNA sugars and the orientation of the intercalated C.C+ pairs result in a modest widening of the narrow grooves at the steps where the hydroxyl groups are in close contact. The free energy of the RNA i-motif, on average -4 kJ mol(-1) per C.C+ pair, is half of the value found in DNA i-motif structures.
机译:具有胞苷残基的延伸的寡脱氧核苷酸结合成四链结构,即i-基序,其中两个头对尾,插入,平行链的双链体通过半质子化的C.C +对结合在一起。我们研究了用富含C的核糖核酸形成i-基序结构的可能性。研究的四个富含C的RNA r(UC5),r(C5),r(C5U)和r(UC3)在酸性pH下缔合成多个插层结构。 r(UC5)形成两个i-基序结构,它们的插入拓扑不同。我们报告了主要形式的结构研究,并分析了与DNA i-motif的比较发现的微小构象差异。主结构的堆叠拓扑避免了完全插入结构中预期的六个2'-OH / 2'-OH排斥触点之一。 RNA糖的C3'-内切褶皱和插入的C.C +对的定向导致在羟基紧密接触的步骤中狭窄凹槽的适度加宽。每个C.C +对平均RNA i-motif的自由能为-4 kJ mol(-1),是DNA i-motif结构中发现的值的一半。

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