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标题：X-ray analysis of an RNA tetraplex (UGGGGU)4 with divalent Sr2+ ions at subatomic resolution (0.61 Å)
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作者：Junpeng Deng ; Yong Xiong ; Muttaiya Sundaralingam 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2001
卷号：98
期号：24
页码：13665-13670
DOI：10.1073/pnas.241374798
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Four-stranded guanine tetraplexes in RNA have been identified to be involved in crucial biological functions, such as dimerization of retroviral RNA, translational repression, and mRNA turnover. However, the structural basis for these biological processes is still largely unknown. Here we report the RNA tetraplex structure (UGGGGU)4 at ultra-high resolution (0.61 A). The space group is P4212, and cell constants are a = b = 36.16 A and c = 74.09 A. The structure was solved by the multiple-wavelength anomalous dispersion method using a set of three-wavelength data of the isomorphous bromo derivative brUGGGGU and refined to 0.61-A resolution. Each of the four strands in the asymmetric unit forms a parallel tetraplex with symmetry-related molecules. The tetraplex molecules stack on one another in opposite polarity (head-to-head or tail-to-tail) to form a pseudocontinuous column. All of the 5'-end uridines rotate around the backbone of G2, swing out, and form unique octaplexes with the neighboring G tetraplexes, whereas the 3'-end uridines are stacked-in and form uridine tetrads. All of the bases are anti, and the riboses are in the mixed C2'- and C3'-puckering mode. Strontium ions are observed in every other guanine tetrad plane, sitting on the fourfold axis and associated to the eight O6 atoms of neighboring guanine bases in a bipyramidal-antiprism geometry. The hydrogens are clearly observed in the structure.
关键词：ultra-high resolution|uridine tetrad|octad