THERMAL UNFOLDING OF A GROUP-I RIBOZYME - THE LOW-TEMPERATURE TRANSITION IS PRIMARILY DISRUPTION OF TERTIARY STRUCTURE
THERMAL UNFOLDING OF A GROUP-I RIBOZYME - THE LOW-TEMPERATURE TRANSITION IS PRIMARILY DISRUPTION OF TERTIARY STRUCTURE
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DOI：
10.1021/bi00052a021
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发表时间：
1993-01-12
期刊：
影响因子：
2.9
通讯作者：
TURNER, DH
中科院分区：
文献类型：
--
作者：
BANERJEE, AR;JAEGER, JA;TURNER, DH
对RNA的折叠途径知之甚少。一种特别有趣的RNA是L-21 Sca I，一种来自嗜热四膜虫大亚基（LSU）rRNA前体的自剪接内含子的线性形式。在pH 7.5的50 mM Na+和10 mM游离Mg 2+中，通过UV吸收和化学作图研究L-21 Sca I的热去折叠。UV熔融实验确定了两个主要的转变，在65和73 ℃下具有最大值。在第一次转变的开始和中间的化学绘图表明，它主要涉及三级结构的破坏。系统发育比较表明L2.1和L9.1a环之间可能存在三级相互作用。化学作图和熔融实验的截断形式的内含子缺乏P9.1a，L-21 Nhe I，与这一假设是一致的。结果表明，升高温度在破坏二级结构之前破坏三级相互作用。这表明在这种情况下，三级相互作用比二级相互作用弱。这些结果支持了RNA结构预测的一个重要假设：二级结构主导折叠自由能。
Little is known about the folding pathways of RNA. A particularly interesting RNA is L-21 Sca I, a linear form of the self-splicing intron from the precursor of the Tetrahymena thermophila large subunit (LSU) rRNA. Thermal unfolding of L-21 Sca I is studied by UV absorption and chemical mapping in 50 mM Na+ and 10 mM free Mg2+ at pH 7.5. UV melting experiments identify two major transitions with maxima at 65 and 73-degrees-C. Chemical mapping at the beginning and middle of the first transition suggests it primarily involves disruption of tertiary structure. Phylogenetic comparisons suggest a potential tertiary interaction between loops L2.1 and L9.1a. Chemical mapping and melting experiments on a truncated form of the intron lacking P9.1a, L-21 Nhe I, are consistent with this hypothesis. The results indicate that increasing temperature disrupts tertiary interations before disrupting secondary structure. This suggests tertiary interactions are weaker than secondary interactions in this case. These results support an important assumption for RNA structure prediction: that secondary structure dominates the free energy of folding.