Mechanism of Aminoacyl-tRNA Synthetases: Recognition and Proofreading Processes

Abstract

Over a decade has elapsed since it became clear that tRNA is specifically aminoacylated by the cognate aminoacyl-tRNA synthetase to provide the correct aminoacyl-tRNA as a building block for protein biosynthesis (Loftfield 1972; Goddard 1978). Despite many attempts, both theoretical and practical, to understand the pathways leading to the final, error-free product formation, there have been until recently only a few experimental facts with which to approach this all-important aspect of aminoacyl-tRNA synthetase function.

The problem is conveniently divisible into two parts. Concerning the small substrate, the amino acid, structural differences may be envisaged as playing a part in the recognition. On the other hand, with regard to tRNA recognition, initial studies were aimed at determining structural differences within the group of ligands and were, perhaps with hindsight, predictably unsuccessful in the search for a recognition region unique to each tRNA. In recent years, partly by abandoning preconceived ideas and recognition theories, great progress has been made in achieving a clearer, semimolecular picture of the processes involved. These new approaches, with their associated jargon (i.e., proofreading, editing, mopping up, triggering, etc.), have revived the interest in the general field of accuracy with a rapid increase in new data that need to be integrated into the framework of previously known facts.

We have recently reviewed the field of aminoacyl-tRNA synthetase specificity up to the beginning of 1977 (Igloi and Cramer 1978). We now discuss new results and interpretations with the hope of obtaining a more up-to-date survey of this important area.