NMR AND MOLECULAR MODELING EVIDENCE FOR A G.A MISMATCH BASE PAIR IN A PURINE-RICH DNA DUPLEX
NMR AND MOLECULAR MODELING EVIDENCE FOR A G.A MISMATCH BASE PAIR IN A PURINE-RICH DNA DUPLEX
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DOI：
10.1073/pnas.88.1.26
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发表时间：
1991-01-01
影响因子：
11.1
通讯作者：
WILSON, WD
中科院分区：
文献类型：
--
作者：
LI, Y;ZON, G;WILSON, WD
H-1核磁共振实验表明，低聚物5‘-d（ATGAGCGAATA）与4个G.A碱基对（下划线）和一个3’未配对的腺苷形成罕见的10碱基对双相结构。核磁共振结果表明，ga错配的鸟苷亚胺质子不是氢键，而是在螺旋结构中堆积。G -> I在两个G - A碱基对上的取代导致双相稳定性的急剧下降，这表明鸟苷氨基的氢键是关键的。核超豪瑟效应光谱（NOESY）和二维相关光谱（COSY）结果表明，其整体双象属于b族。在二维NOESY光谱中，错配的AH2与另一个错配碱基对的AH1′之间以及错配的GH8与另一个错配碱基对的GNH1之间的交叉链NOEs建立了嘌呤-嘌呤叠加模式，即腺苷上腺苷和鸟苷上鸟苷，这有力地稳定了双链结构。利用含有A- nh -2 - GN3和G-NH-2 - AN7氢键的g - A碱基对和G-NH-2 - AN7氢键的g - A碱基对，以及g - A碱基对两侧的b型碱基对，构建了该不寻常双相化合物的计算机图形分子模型[5d (ATGAGC)]。能量最小化双工满足NOESy和COSY结果的所有实验约束。预测错配的G-NH-2与磷酸氧形成氢键。
H-1 NMR experiments indicate that the oligomer 5'-d(ATGAGCGAATA) forms an unusual 10-base-pair duplex with 4 G.A base pairs (underlined) and a 3' unpaired adenosine. NMR results indicate that guanosine imino protons of the G.A mismatches are not hydrogen bonded but are stacked in the helix. A G --> I substitution in either G.A base pair causes a dramatic decrease in duplex stability and indicates that hydrogen bonding of the guanosine amino group is critical. Nuclear Overhauser effect spectroscopy (NOESY) and two-dimensional correlated spectroscopy (COSY) results indicate that the overall duplex conformation is in the B-family. Cross-strand NOEs in two-dimensional NOESY spectra between a mismatched AH2 and an AH1' of the other mismatched base pair and between a mismatched GH8 and GNH1 of the other mismatch establish a purine-purine stacking pattern, denosine over adenosine and guanosine over guanosine, which strongly stabilizes the duplex. A computer graphics molecular model of the unusual duplex was constructed with G.A base pairs containing A-NH-2 to GN3 and G-NH-2 to AN7 hydrogen bonds and B-form base pairs on both sides of the G.A pairs [5'd(ATGAGC)]. The energy-minimized duplex satisfies all experimental constraints from NOESy and COSY results. A hydrogen bond from G-NH-2 of the mismatch to a phosphate oxygen is predicted.