Aymami J, Coll M, Frederick C A, Wang A H, Rich A
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Nucleic Acids Res. 1989 Apr 25;17(8):3229-45. doi: 10.1093/nar/17.8.3229.
Physical properties of the DNA duplex, poly(dA).poly(dT) differ considerably from the alternating copolymer poly(dAT). A number of molecular models have been used to describe these structures obtained from fiber X-ray diffraction data. The recent solutions of single crystal DNA dodecamer structures with segments of oligo-A.oligo-T have revealed the presence of a high propeller twist in the AT regions which is stabilized by the formation of bifurcated (three-center) hydrogen bonds on the floor of the major groove, involving the N6 amino group of adenine hydrogen bonding to two O4 atoms of adjacent thymine residues on the opposite strand. Here we show that it is possible to incorporate the features of the single crystal analysis, specifically high propeller twist, bifurcated hydrogen bonds, and a narrow minor groove, as well as the close interstrand NMR signal between adenine HC2 and ribose HC1' of the opposite strand, into a model that is fully compatible with the diffraction data obtained from poly(dA).poly(dT).
DNA双链体poly(dA).poly(dT)的物理性质与交替共聚物poly(dAT)有很大差异。许多分子模型已被用于描述从纤维X射线衍射数据获得的这些结构。最近对含有寡聚A.寡聚T片段的单晶DNA十二聚体结构的解析揭示,在AT区域存在高螺旋桨扭转,这通过在大沟底部形成分叉(三中心)氢键得以稳定,其中腺嘌呤的N6氨基与相反链上相邻胸腺嘧啶残基的两个O4原子形成氢键。在此我们表明,有可能将单晶分析的特征,特别是高螺旋桨扭转、分叉氢键和狭窄的小沟,以及相反链上腺嘌呤HC2与核糖HC1'之间紧密的链间核磁共振信号,纳入一个与从poly(dA).poly(dT)获得的衍射数据完全兼容的模型中。