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首页> 外文期刊>Biochemistry >Determinants of DNA quadruplex structural type: sequence and potassium binding.
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Determinants of DNA quadruplex structural type: sequence and potassium binding.

机译：DNA四链体结构类型的决定因素：序列和钾结合。

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There are DNA sequences which adopt the same quadruplex structural type in the presence of sodium as in the presence of sodium and potassium. There are also sequences that appear to have a requirement for the presence of potassium for the adoption of a particular quadruplex structural type. Information about the basis for these potassium effects has been obtained by examining the structures of a set of DNAs with differing numbers of loop residues and different lengths of runs of dG residues in the presence of sodium alone and in the presence of potassium and sodium. On the basis of the results, obtained primarily via solution-state NMR, it appears that very small loops favor parallel stranded quartet structures which do not require the presence of potassium. DNAs with loops of two to four residues and runs of two dG residues can form quadruplex structures of the "edge" or "chair" type in the presence of potassium but not in the presence of sodium alone. When all of the loops contain four residues, a "crossover" or "basket" type structure can be formed in the presence of sodium as well as in the presence of sodium and potassium. Structures with runs of three or four dG residues and with loops from two to four residues can form basket or crossover type structures in the absence of potassium. The presence of a purine in a loop can block both potassium binding and formation of chair type structures. Modeling of the interactions of cations with these quadruplex structures indicates that the potassium ions required for chair type structures interact with a terminal quartet and residues in the adjacent loop.
机译：存在在钠存在下与在钠和钾存在下采用相同四链体结构类型的DNA序列。对于采用特定的四链体结构类型，似乎也需要钾的存在。关于这些钾效应基础的信息，是通过在单独的钠存在下以及在钾和钠存在下检查一组具有不同环残基数量和不同dG残基游程长度的DNA的结构而获得的。基于主要通过溶液态NMR获得的结果，似乎非常小的环倾向于不需要钾存在的平行链四方结构。具有两个至四个残基的环并且具有两个dG残基的DNA可以在钾存在下形成钠盐或“椅子”型四链体结构，而在钠单独存在下则不能。当所有环含有四个残基时，在钠存在下以及在钠和钾存在下可形成“交联”或“篮子”型结构。在没有钾的情况下，具有三个或四个dG残基的结构以及具有两个至四个残基的环的结构可以形成篮状或交叉型结构。环中存在嘌呤可同时阻断钾结合和椅子型结构的形成。阳离子与这些四链体结构相互作用的模型表明，椅子型结构所需的钾离子与末端四重奏和相邻环中的残基相互作用。

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