Structure and Function of tRNA and Aminoacyl tRNA Synthetases in Eukaryotes

Abstract

In both prokaryotes and eukaryotes, transfer RNA (tRNA) occupies a central position in protein synthesis because it serves as the translator of the genetic message. It does this by acting as an adapter to convert the small structural differences among amino acids into a clearly distinct form capable of reading the specifying sequence of ribonucleotides in the mRNA. The need for such an adapter was recognized long ago (1; reviewed in 2), and it is instructive to note that even at that time the basic elements of tRNA and the aminoacylation process were recognized. Thus, tRNAs were postulated to be a set of specific oligonucleotides, 3–6 residues in length, which would be enzymatically attached to their amino acids, by a corresponding set of enzymes capable of selecting out both the given amino acid and its cognate oligonucleotide adapter from all others. The triplet codon would then be read by base-pairing with three of the adapter nucleotides (the anticodon). Crick (1) further suggested that the nature of the link between the amino acid and adapter would likely provide the energy for amino acid polymerization. Except for a failure to appreciate the ribosome binding function of tRNA which required a considerably larger molecule, this hypothesis proposed even before the existence of tRNA was known has proven to be surprisingly accurate in its description of the role of tRNA and aminoacyl-tRNA synthetases in protein synthesis.