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首页> 外文期刊>Biochemistry >Structural Dynamics of a Mitochondrial tRNA Possessing Weak Thermodynamic Stability
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Structural Dynamics of a Mitochondrial tRNA Possessing Weak Thermodynamic Stability

机译：线粒体tRNA具有弱热力学稳定性的结构动力学

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摘要

Folding dynamics are ubiquitously involved in controlling the multivariate functions of RNAs. While the high thermodynamic stabilities of some RNAs favor purely native states at equilibrium, it is unclear whether weakly stable RNAs exist in random, partially folded states or sample well-defined, globally folded conformations. Using a folding assay that precisely tracks the formation of native aminoacylable tRNA, we show that the folding of a weakly stable human mitochondrial (hmt) leucine tRNA is hierarchical with a distinct kinetic folding intermediate. The stabilities of the native and intermediate conformers are separated by only about 1.2 kcal/mol, and the species are readily interconvertible. Comparison of folding dynamics between unmodified and fully modified tRNAs reveals that post-transcriptional modifications produce a more constrained native structure that does not sample intermediate conformations. These structural dynamics may thus be crucial for recognition by some modifying enzymes in vivo, especially those targeting the globular core region, by allowing access to pretransition state conformers. Reduced conformational sampling of the native, modified tRNAs could then permit improved performance in downstream processes of translation. More generally, weak stabilities of small RNAs that fold in the absence of chaperone proteins may facilitate conformational switching that is central to biological function.
机译：折叠动力学普遍涉及控制RNA的多元功能。尽管某些RNA的高热力学稳定性有利于处于平衡状态的纯天然状态，但尚不清楚弱稳定的RNA是否以随机，部分折叠的状态存在或是否存在样品定义明确的全局折叠的构象。使用精确跟踪天然氨基酰基tRNA形成的折叠分析，我们显示了弱稳定的人类线粒体（hmt）亮氨酸tRNA的折叠具有独特的动力学折叠中间体。天然和中间构象异构体的稳定性仅相差约1.2 kcal / mol，并且该物种易于相互转化。比较未修饰的和完全修饰的tRNA之间的折叠动力学，发现转录后修饰产生了更受约束的天然结构，无法采样中间构象。因此，这些结构动力学对于通过体内的某些修饰酶（尤其是那些靶向球状核心区域的修饰酶）进行识别而至关重要，因为它们可以进入过渡前状态构象异构体。天然的，修饰的tRNA的构象取样减少，然后可以改善下游翻译过程中的性能。更一般而言，在不存在伴侣蛋白的情况下折叠的小RNA的弱稳定性可能有助于构象转换，而构象转换对于生物学功能至关重要。

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