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首页> 外文期刊>Biochemistry >Conformational transitions of an unmodified tRNA: Implications for RNA folding
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Conformational transitions of an unmodified tRNA: Implications for RNA folding

机译：未修饰的tRNA的构象转变：对RNA折叠的影响。

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Unmodified tRNAs are powerful systems to study the effects of posttranscriptional modifications and site-directed mutations on both the structure and function of these ribonucleic acids. To define the general limitations of synthetic constructs as models for native tRNAs, it is necessary to elucidate the conformational states of unmodified tRNAs as a function of solution conditions. Here we report the conformational properties of unmodified yeast tRNA(Phe) as a function of ionic strength, [Mg2+], and temperature using a combination of spectroscopic measurements along with chemical and enzymatic probes. We find that in low [Naf] buffer at low temperature, native yeast tRNAPhe adopts tertiary structure in the absence of Mg2+. By contrast, tertiary folding of unmodified yeast tRNA(Phe) has an absolute requirement for Mg2+. Below the melting temperature of the cloverleaf, unmodified yeast tRNAPhe exists in a Mg2+ dependent equilibrium between secondary and tertiary structure. Taken together, our findings suggest that although the tertiary structures of tRNAs are broadly comparable, the intrinsic stability of the tertiary fold, the conformational properties of intermediate states, and the stability of intermediate states can differ significantly between tRNA sequences. Thus, the use of unmodified tRNAs as models for native constructs can have significant limitations. Broad conclusions regarding "tRNA folding" as a whole must be viewed cautiously, particularly in cases where structural changes occur, such as during protein synthesis. [References: 83]
机译：未修饰的tRNA是研究转录后修饰和定点突变对这些核糖核酸的结构和功能的影响的强大系统。为了定义合成构建体作为天然tRNA模型的一般局限性，有必要阐明未修饰tRNA的构象状态与溶液条件的关系。在这里，我们结合光谱测量以及化学和酶促探针的应用，报告了未修饰的酵母tRNA（Phe）的构象性质随离子强度，[Mg2 +]和温度的变化。我们发现在低温下[Naf]低缓冲液中，天然酵母tRNAPhe在没有Mg2 +的情况下采用三级结构。相比之下，未经修饰的酵母tRNA（Phe）的三级折叠对Mg2 +具有绝对的要求。在三叶草的熔化温度以下，未修饰的酵母tRNAPhe存在于二级和三级结构之间的Mg2 +依赖性平衡中。两者合计，我们的发现表明，尽管tRNA的三级结构具有广泛的可比性，但tRNA序列之间的三重折叠的固有稳定性，中间状态的构象性质以及中间状态的稳定性可能会显着不同。因此，使用未修饰的tRNA作为天然构建体的模型可能会有很大的局限性。关于“ tRNA折叠”整体的广泛结论必须谨慎对待，尤其是在发生结构变化的情况下，例如在蛋白质合成过程中。 [参考：83]

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