Premraj B J, Patel P K, Kandimalla E R, Agrawal S, Hosur R V, Yathindra N
Department of Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai, 600 025, India.
Biochem Biophys Res Commun. 2001 May 11;283(3):537-43. doi: 10.1006/bbrc.2001.4828.
In order to provide a structural basis for the unusual properties of 2',5' nucleic acids, especially their unsuitability as information molecules, we report here a high resolution NMR structure of a 2',5' RNA fragment r(GCCGCGGC). It forms an A type duplex with C2'endo compact nucleotide repeat, instead of the familiar C3'endo compact nucleotide (seen in RNA) supporting the deductions made earlier from stereochemical considerations. This data together with the observation that 2',5' nucleic acids require mandatory slide and displacement for duplex and triplex structure formation suggest their reluctance to form the biologically relevant B type duplex. It is argued that this lack of flexibility for helical polymorphism and other inadequacies as a consequence of this may be a contributing factor for the rejection of 2',5' links by nature. The structure exhibits interesting features such as the syn glycosyl conformation for the terminal guanine and a hydrogen bond between O3' hydroxyl and anionic oxygen of the phosphate.
为了给2',5'核酸的异常特性,尤其是其作为信息分子的不适用性提供结构基础,我们在此报告一个2',5' RNA片段r(GCCGCGGC)的高分辨率核磁共振结构。它形成了一种具有C2'内型紧凑核苷酸重复的A型双链体,而不是常见的C3'内型紧凑核苷酸(在RNA中可见),这支持了早期从立体化学考虑得出的推论。这些数据,连同2',5'核酸形成双链体和三链体结构需要强制滑动和位移的观察结果,表明它们不愿意形成生物学上相关的B型双链体。有人认为,这种螺旋多态性缺乏灵活性以及由此产生的其他不足之处可能是自然界排斥2',5'连接的一个促成因素。该结构展现出有趣的特征,如末端鸟嘌呤的顺式糖基构象以及O3'羟基与磷酸根阴离子氧之间的氢键。