Structure, internal motions and association-dissociation kinetics of the i-motif dimer of d(5mCCTCACTCC).
Structure, internal motions and association-dissociation kinetics of the i-motif dimer of d(5mCCTCACTCC).
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DOI：
10.1093/nar/gki843
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发表时间：
2005
影响因子：
14.9
通讯作者：
Leroy, JL
中科院分区：
文献类型：
--
作者：
Canalia, M;Leroy, JL
在微酸性pH下，两条d（5 mCCTCACTCC）链的缔合导致i基序二聚体的形成。用核磁共振方法研究了[d（5 mCCTCACTCC）]2，堆积在i基序核心中的碱基对的内部运动，二聚体形成和解离动力学对pH的关系。1H和31 P光谱的优异分辨率提供了二面角的测定，其与大量的距离限制一起，通过与先前的i-基序结构的NMR研究相比，实质上改进了糖-磷酸骨架的定义。[d（5 mCCTCACTCC）]2是由六个对称的C·C+对和T7·T7对结合在一起的两个对称发夹插入而形成的。由单个残基A5形成的发夹环穿过i基序核心同一侧的窄槽。碱基对嵌入顺序为C9·C9+/5 mC 1·5 mC 1 +/C8·C8+/C2·C2+/T7·T7/C6·C6+/C4·C4+。T3的基地是翻转出在宽槽。该结构的核心包括四个长寿命对，其在15°C下的寿命从100 s（C8·C8+）到0.18 s（T7·T7）不等。在pH 6.8和4.8之间测量[d（5 mCCTCACTCC）]2的形成速率和寿命。二聚体的形成速率比B-DNA双链体慢三到四个数量级。它取决于pH值，因为它必须发生在涉及中性和质子化残基的非合作缔合的双分子过程中。在所研究的pH范围内，二聚体的寿命（0°C，pH 6.8时为500 s）约随10−pH值变化。
At slightly acidic pH, the association of two d(5mCCTCACTCC) strands results in the formation of an i-motif dimer. Using NMR methods, we investigated the structure of [d(5mCCTCACTCC)]2, the internal motion of the base pairs stacked in the i-motif core, the dimer formation and dissociation kinetics versus pH. The excellent resolution of the 1H and 31P spectra provided the determination of dihedral angles, which together with a large set of distance restraints, improve substantially the definition of the sugar-phosphate backbone by comparison with previous NMR studies of i-motif structures. [d(5mCCTCACTCC)]2 is built by intercalation of two symmetrical hairpins held together by six symmetrical C•C+ pairs and by pair T7•T7. The hairpin loops that are formed by a single residue, A5, cross the narrow grooves on the same side of the i-motif core. The base pair intercalation order is C9•C9+/5mC1•5mC1+/C8•C8+/C2•C2+/T7.T7/C6•C6+/C4•C4+. The T3 bases are flipped out in the wide grooves. The core of the structure includes four long-lived pairs whose lifetimes at 15°C range from 100 s (C8•C8+) to 0.18 s (T7•T7). The formation rate and the lifetime of [d(5mCCTCACTCC)]2 were measured between pH 6.8 and 4.8. The dimer formation rate is three to four magnitude orders slower than that of a B-DNA duplex. It depends on pH, as it must occur for a bimolecular process involving non cooperative association of neutral and protonated residues. In the range of pH investigated, the dimer lifetime, 500 s at 0°C, pH 6.8, varies approximately as 10−pH.
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影响因子：
14.9
作者：
HIRAO, I;KAWAI, G;MIURA, K
通讯作者：
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