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Indirect readout of tRNA for aminoacylation

机译：间接读出tRNA进行氨基酰化

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Aminoacylation of tRNA by aminoacyl-tRNA synthetases is the essential reaction that matches protein amino acids with the trinucleotide sequences specified in mRNA. Direct electrostatic interactions made by tRNA synthetases with discriminating functional groups on the tRNA bases have long been known to determine aminoacylation specificity. However, structural and biochemical studies have revealed a second "indirect readout" mechanism that makes an important contribution as well. In indirect readout, the sequence-dependent conformations of tRNA are recognized through protein contacts with the sugarphosphate backbone and with nonspecific portions of the bases. This mechanism appears to function in single-stranded regions, in canonical A-type duplex segments, and in the complex tertiary core portion of the tRNA. Operation of the indirect mechanism is not exclusive of the direct mechanism, and both are further mediated by induced-fit rearrangements, in which enzyme and IRNA undergo precise conformational changes after formation of an initial encounter complex. The examples of indirect readout in tRNA synthetase complexes extend the concept beyond its traditional application to DNA duplexes and serve as models for the operation of this mechanism in more complex systems such as the ribosome.
机译：通过氨酰基-tRNA合成酶将tRNA进行氨酰化是将蛋白质氨基酸与mRNA中指定的三核苷酸序列相匹配的基本反应。长期以来，已知由tRNA合成与tRNA碱基上的区分性官能团进行的直接静电相互作用可确定氨酰化的特异性。然而，结构和生化研究揭示了第二种“间接读出”机制，该机制也做出了重要贡献。在间接读出中，通过与糖磷酸骨架和碱基的非特异性部分的蛋白质接触，可以识别tRNA的序列依赖性构象。此机制似乎在单链区域，规范的A型双链体区段以及tRNA的复杂三级核心部分中起作用。间接机制的运行并不排除直接机制，而且两者都由诱导拟合重排介导，在这种情况下，酶和IRNA在形成初始相遇复合物后会发生精确的构象变化。在tRNA合成酶复合物中间接读出的例子将其概念扩展到了传统的DNA双链体以外，并在更复杂的系统（如核糖体）中用作该机制的模型。

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