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首页> 外文期刊>Biochemistry >Solution structure of the aminofluorene [AF]-intercalated conformer of the syn-[AF]-C-8-dG adduct opposite dC in a DNA duplex
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Solution structure of the aminofluorene [AF]-intercalated conformer of the syn-[AF]-C-8-dG adduct opposite dC in a DNA duplex

机译：DNA双链体中与dC相对的syn- [AF] -C-8-dG加合物的氨基芴[AF]插入构象异构体的溶液结构

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We report below on a conformational equilibrium between AF-intercalated and AF-external states in slow exchange for the [AF]dG lesion positioned opposite dC in the d(C-[AF]G-C) d(G-C-G) sequence context, The slow exchange between states is attributed to interconversion between syn glycosidic torsion angle in the AF-intercalated and anti torsion angle in AF-external conformers of the [AF]dG opposite dC containing duplex. The present paper describes an NMR-molecular mechanics study that defines the solution structure of the AF-intercalated conformer for the case of [AF]dG adduct positioned opposite dC in the d(C-[AF]G-C).d(G-C-G) sequence context. The structure is of the base displacement-intercalation type where the aminofluorene ring is intercalated into the helix between intact Watson-Crick dG.dC base pairs, which results in a displacement of the modified guanine ring into the major groove where it stacks with the major groove edge of its 5'-flanking cytosine in the adduct duplex. The conformational equilibrium between AF-intercalated conformer (similar to 70%) with a syn alignment and AF-external conformer (similar to 30%) with an anti alignment for the [AF]dG adduct positioned opposite dC in the d(C-[AF]G-C).d(G-C-G) sequence context can be contrasted with our earlier demonstration that the population is 100% for the AP-intercalated conformer with a syn alignment at the N-(deoxyguanosin-8-yl)-2-aminopyrene ([AP]dG) adduct site positioned opposite dC in the same sequence context [Mao, B,, Vyas, R. R., Hingerty, B, E,, Broyde, S,, Basu, A, K., and Patel, D, J. (1996) Biochemistry, 35, 12659-12670]. This shift in population may reflect the much larger size of the pyrenyl ring of the [AP]dG adduct compared to the fluorenyl ring of the [AF]dG adduct which in turn might provide for a greater overlap of the aromatic amine with the flanking base pairs in the intercalated conformer of the former adduct in DNA. [References: 53]
机译：我们在下面报告了在d（C- [AF] GC）d（GCG）序列上下文中与dC相对的[AF] dG病变缓慢交换的AF插入状态与AF外部状态之间的构象平衡，状态之间的差异归因于[AF] dG相对于含dC的双链体的[AF] dG的AF外部构象体中AF插入的同糖苷扭转角和抗扭转角之间的相互转换。本文描述了NMR分子力学研究，该研究定义了d（C- [AF] GC）.d（GCG）序列中与dC相对的[AF] dG加合物的情况下，AF插入构象体的溶液结构。上下文。该结构为碱基置换嵌入型，其中氨基芴环插入完整的Watson-Crick dG.dC碱基对之间的螺旋中，这导致修饰的鸟嘌呤环置换入主要凹槽，并与主要碱基堆叠加合物双链体中其5'侧胞嘧啶的凹槽边缘。对于位于d（C- [d]中与dC相对的[AF] dG加合物，AF插入构象异构体（大约70％）具有同向比对和AF外部构象异构体（近似30％）具有反比对之间的构象平衡。 AF] GC）.d（GCG）序列的背景可以与我们之前的研究结果进行对比，即AP插入的构象体的种群为100％，在N-（脱氧鸟苷-8-基）-2-氨基py上具有同义比对（ [AP] dG）加合物位点，在同一序列背景下与dC相对[Mao，B，Vyas，RR，Hingerty，B，E，Broyde，S，Basu，A，K。和Patel，D，J （1996）Biochemistry，35，12659-12670]。与[AF] dG加合物的芴基环相比，这种人口迁移可能反映了[AP] dG加合物的pyr环的尺寸大得多，这反过来又可能提供芳族胺与侧基的更大重叠在DNA中前加合物的插入构象异构体中配对。 [参考：53]

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