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Origins and early evolution of the translation machinery

机译：翻译机器的起源和早期演变

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The modern ribosome is a complex biological machine that is responsible for chiral synthesis of cellular proteins according to the genetic code as specified by a mRNA. Major portions of the ribosomal machinery were likely in place before the last universal common ancestor (LUCA) of life. The early evolution of the ribosome has implications for the origin of the genetic code, the emergence of chirality in peptide synthesis, and the emergence of LUCA. Although codon assignments may remain a mystery, the history of the ribosome provides a context for dating the first usage of mRNA. In the case of chirality, the modern ribosome suggests that a small initial chiral preference for L-amino acids in the environment may have been greatly enhanced by a two step process in which the charging of a primitive tRNA and the subsequent synthesis of a peptide bond both had the same chiral preference. The resulting ability to make largely chiral peptides may have provided an advantage over other prebiotic mechanisms for making peptides. Finally, the late addition of factors such as EF-G may have greatly accelerated the emerging ribosome's ability to synthesize proteins, thereby allowing entities with this novel capability to emerge as the LUCA.
机译：现代核糖体是一个复杂的生物机器，负责根据mRNA指定的遗传密码手性合成细胞蛋白。核糖体机制的主要部分可能在生命的最后一个普遍祖先（LUCA）之前就位。核糖体的早期进化对遗传密码的起源，肽合成中的手性的出现以及LUCA的出现都具有影响。尽管密码子分配可能仍然是一个谜，但核糖体的历史为首次使用mRNA提供了背景。在手性的情况下，现代核糖体表明通过两步过程可以大大增强环境中对L-氨基酸的少量初始手性偏好，在该过程中，原始tRNA的充电和随后肽键的合成两者具有相同的手性偏好。所得的主要制备手性肽的能力可能提供了优于其他制备肽的益生元机制的优势。最后，诸如EF-G等因素的后期添加可能大大加快了新兴核糖体合成蛋白质的能力，从而使具有这种新能力的实体成为LUCA。

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