THE DNA STRAND IN DNA.RNA HYBRID DUPLEXES IS NEITHER B-FORM NOR A-FORM IN SOLUTION
THE DNA STRAND IN DNA.RNA HYBRID DUPLEXES IS NEITHER B-FORM NOR A-FORM IN SOLUTION
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DOI：
10.1021/bi00067a007
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发表时间：
1993-04-27
期刊：
影响因子：
2.9
通讯作者：
REID, BR
中科院分区：
文献类型：
--
作者：
SALAZAR, M;FEDOROFF, OY;REID, BR
DNA.RNA 杂交体 (GTCACATG).(caugugac) 的结构（其中小写字母表示 RNA 残基）已根据 J 偶联分析和 2D-NOE 研究确定。该序列中的中心六聚体之前已被研究过 [Reid, D. G.、Salisbury, S. A.、Brown, T.、Williams, D. H.、Vasseur, J.-J.、Rayner, B. 和 Imabach, J.-L.。 (I 983) 欧元。 J.生物化学。 135, 307-314] 通过一维 NOE 方法和圆二色性研究。与他们的结果相反，我们发现该双链体在溶液中不呈现 B 型构象。相反，RNA 残基保留其 C3'-endo（A 型）构象，如不存在 H1'-H2' 偶联以及强 H6/H8 与 (n - 1) H2' NOE 所示。另一方面，DNA 残基的糖不呈现 A 型（或 B 型）构象，而是呈现 O4'-endo 范围内的中间构象（P 几乎等于 72-110 度），如强 H1'-H4' NOE、中等强度 H2''-H3' COSY 交叉峰、强 H3'-H4' DQF-COSY 交叉的存在所示。峰，以及与 H1'-H2'' 耦合常数大小大致相同的 H1'-H2' 耦合常数。这些结果表明RNA链不仅保留其N型结构，而且对DNA链的构象产生影响。我们的结果提供了强有力的证据，证明 DNA.RNA 杂合双链体并不呈现全 C2'-endo B 型构象；它们在溶液中也不呈现全C3'-endo A型构象。此外，虽然不是本研究的主要焦点，但 DNA 和 RNA 残基的纵向弛豫时间的比较表明，杂合双链体的二维 NMR 谱需要延长弛豫延迟，正如之前在 DNA.RNA 嵌合双链体中观察到的那样（Wang, A. C.、Kim, S.-G.、Chou, S.-H.、Orban, J.、Flynn, P. 和 Reid, B. R. (1992) 生物化学） 31、3940-3946）。
The structure of the DNA.RNA hybrid (GTCACATG).(caugugac), where lowercase letters designate RNA residues, has been determined on the basis of J-coupling analysis and 2D-NOE studies. The central hexamer in this sequence has been previously studied [Reid, D. G., Salisbury, S. A., Brown, T., Williams, D. H., Vasseur, J.-J., Rayner, B., & Imabach, J.-L. (I 983) Eur. J. Biochem. 135, 307-314] via one-dimensional NOE methods and circular dichroism studies. Contrary to their results, we find that this duplex does not assume a B-form conformation in solution. Instead, the RNA residues retain their C3'-endo (A-form) conformation, as indicated by the absence of H1'-H2' couplings and by strong H6/H8 to (n - 1) H2' NOEs. The sugars of the DNA residues, on the other hand, do not assume an A-form (or a B-form) conformation but an intermediate conformation in the O4'-endo range(P almost-equal-to 72-110-degrees), as indicated by the presence of strong H1'-H4' NOEs, medium-strength H2''-H3' COSY cross peaks, strong H3'-H4' DQF-COSY cross peaks, and H1'-H2' coupling constants that are of approximately the same magnitude as the H1'-H2'' coupling constants. These results suggest that the RNA strand not only retains its N-type structure but also exerts an influence on the conformation of the DNA strand. Our results provide strong evidence that DNA.RNA hybrid duplexes do not assume an all-C2'-endo B-type conformation; neither do they assume an all-C3'-endo A-type conformation in solution. Furthermore, although not the main focus of this study, a comparison of the longitudinal relaxation times of the DNA and RNA residues indicates the need for extended relaxation delays in two-dimensional NMR spectra of hybrid duplexes, as has been previously observed for DNA.RNA chimeric duplexes (Wang, A. C., Kim, S.-G., Chou, S.-H., Orban, J., Flynn, P., & Reid, B. R. (1992) Biochemistry 31, 3940-3946).