Katahira M, Kanagawa M, Sato H, Uesugi S, Fujii S, Kohno T, Maeda T
Department of Bioengineering, Faculty of Engineering, Yokohama National University, Japan.
Nucleic Acids Res. 1994 Jul 25;22(14):2752-9. doi: 10.1093/nar/22.14.2752.
The thermal stability and structure of an RNA duplex, r(GGACGAGUCC)2, the base sequence of which was modelled after both a hammerhead ribozyme and a lead ribozyme, were studied by CD and NMR. We previously demonstrated that the corresponding DNA duplex, d(GGACGAGTCC)2, formed unique 'sheared' G:A base pairs, where an amino proton, instead of an imino proton, of G is involved in the hydrogen bonding, and G and A bases are arranged 'side by side' instead of 'head to head' (Nucleic Acids Res. (1993) 21, 5418-5424). CD melting profiles showed that the RNA duplex is thermally more stable than the corresponding DNA duplex. NMR studies revealed that sheared G:A base pairs are formed in the RNA duplex, too, although the overall structure of the RNA is the A form, which differs from the B form taken on by the corresponding DNA. A model building study confirmed that sheared G:A base pairs can be accommodated in the double helical structure of the A form. A difference between the RNA and DNA duplexes in the stacking interaction involving G:A mismatch bases is also suggested. The demonstration that sheared G:A base pairs can be formed not only in DNA but also in RNA suggests that this base pairing plays an important role regarding the RNA structure.
对RNA双链体r(GGACGAGUCC)₂的热稳定性和结构进行了研究，其碱基序列是以锤头状核酶和铅核酶为模板构建的，采用圆二色光谱（CD）和核磁共振（NMR）技术。我们之前证明，相应的DNA双链体d(GGACGAGTCC)₂形成了独特的“剪切”G:A碱基对，其中G的氨基质子而非亚氨基质子参与氢键形成，G和A碱基“并排”排列而非“头对头”排列（《核酸研究》（1993年）21卷，5418 - 5424页）。CD熔解曲线表明，该RNA双链体比相应的DNA双链体热稳定性更高。NMR研究显示，RNA双链体中也形成了剪切G:A碱基对，尽管RNA的整体结构为A构象，这与相应DNA的B构象不同。模型构建研究证实，剪切G:A碱基对可容纳于A构象的双螺旋结构中。还表明了RNA和DNA双链体在涉及G:A错配碱基的堆积相互作用方面存在差异。剪切G:A碱基对不仅能在DNA中形成，也能在RNA中形成，这一证明表明这种碱基配对在RNA结构方面起着重要作用。
