Structural aspects and evolutionary implications of the recognition between tRNAs and aminoacyl-tRNA synthetases.

Recent structural discoveries in the fields of tRNAs and aminoacyl-tRNA synthetases (aaRS), such as the existence of two classes of aminoacyl tRNA synthetases, the modular character of aaRS with domains homologous to other existing proteins, and the absence of direct interactions between the catalytic site containing the aminoacid binding pocket and the anticodon point the way to an understanding of the origin of the genetic code.