Consecutive Terminal GU Pairs Stabilize RNA Helices

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• 作者：Mai-Thao Nguyen ; Susan J. Schroeder
• 刊名：Biochemistry
• 出版年：2010
• 出版时间：December 14, 2010
• 年：2010
• 卷：49
• 期：49
• 页码：10574-10581
• 全文大小：844K
• 年卷期：v.49,no.49(December 14, 2010)
• ISSN：1520-4995

文摘

Consecutive GU pairs at the ends of RNA helices provide significant thermodynamic stability between −1.0 and −3.8 kcal/mol at 37 °C, which is equivalent to approximately 2 orders of magnitude in the value of a binding constant. The thermodynamic stabilities of GU pairs depend on the sequence, stacking orientation, and position in the helix. In contrast to GU pairs in the middle of a helix that may be destabilizing, all consecutive terminal GU pairs contribute favorable thermodynamic stability. This work presents measured thermodynamic stabilities for 30 duplexes containing two, three, or four consecutive GU pairs at the ends of RNA helices and a model to predict the thermodynamic stabilities of terminal GU pairs. Imino proton NMR spectra show that the terminal GU nucleotides form hydrogen-bonded pairs. Different orientations of terminal GU pairs can have different conformations with equivalent thermodynamic stabilities. These new data and prediction model will help improve RNA secondary structure prediction, identification of miRNA target sequences with GU pairs, and efforts to understand the fundamental physical forces directing RNA structure and energetics.