A compact RNA tertiary structure contains a buried Backbone-K+ complex
A compact RNA tertiary structure contains a buried Backbone-K+ complex
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DOI：
10.1016/s0022-2836(02)00147-x
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发表时间：
2002-05-10
影响因子：
5.6
通讯作者：
Draper, DE
中科院分区：
文献类型：
--
作者：
Conn, GL;Gittis, AG;Draper, DE
58个核苷酸的核糖体RNA片段的结构将发夹环的几个磷酸基团埋在一个大的三级核心中。在对含有该RNA的X射线晶体结构进行精炼的过程中，发现一个钾离子被掩埋的磷酸基团中的六个氧原子接触；该离子完全包含在RNA的溶剂可及表面内。离子螯合部位的静电势异常大，足以补偿与离子部分脱水和离域离子置换相关的大量能量损失。非常大的预测结合自由能，类似于-30千卡/摩尔，意味着RNA必须占据这个位置才能折叠。这些发现与以前对该RNA三级结构的离子依赖性折叠的研究一致，该研究的结论是，一价离子在部分脱水的环境中结合，在那里镁离子不容易竞争结合。通过用螯合离子补偿掩埋的磷酸基团的不利自由能，RNA能够产生比其他情况下更大、更复杂的第三折叠。(C)2002爱思唯尔科学有限公司。保留所有权利。
The structure of a 58 nucleotide ribosomal RNA fragment buries several phosphate groups of a hairpin loop within a large tertiary core. During refinement of an X-ray crystal structure containing this RNA, a potassium ion was found to be contacted by six oxygen atoms from the buried phosphate groups; the ion is contained completely within the solvent-accessible surface of the RNA. The electrostatic potential at the ion chelation site is unusually large, and more than compensates for the substantial energetic penalties associated with partial dehydration of the ion and displacement of delocalized ions. The very large predicted binding free energy, similar to - 30 kcal/mol, implies that the site must be occupied for the RNA to fold. These findings agree with previous studies of the ion-dependent folding of tertiary structure in this RNA, which concluded that a monovalent ion was bound in a partially dehydrated environment where Mg2+ could not easily compete for binding. By compensating the unfavorable free energy of buried phosphate groups with a chelated ion, the RNA is able to create a larger and more complex tertiary fold than would be possible otherwise. (C) 2002 Elsevier Science Ltd. All rights reserved.