Origins and early evolution of the translation machinery

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.