Proofreading in translation: Dynamics of the double-sieve model
Résumé
The chemical resemblance between amino acids is a major challenge for the fidelity of mRNA translation. The need for a quality-control pathway to distinguish similar amino acids during protein synthesis was already predicted by Linus Pauling (1) in the 1950s before the discovery of the molecular mechanism involved in the process. The article by Hussain et al. (2) in PNAS addresses some aspects of this fundamental problem. Translation of mRNA into proteins involves two key steps of the decoding process. Aminoacyl tRNA synthetases (aaRSs) first translate the genetic code into amino acids and then attach the correct amino acids to their cognate tRNAs. The charged tRNAs are subsequently brought to the ribosomes and positioned on the mRNA, allowing completion of protein synthesis. The aminoacylation reaction itself proceeds in two stages: ( i ) activation of the amino acid by ATP, leading to synthesis of an amino acid adenylate; and ( ii ) charging of the amino acid at the CCA end of the cognate tRNA. Two classes of enzymes with distinct active site structures are responsible for the accuracy of the reaction (3). Editing can occur either before (pretransfer editing) or after (posttransfer editing) a misactivated amino acid is attached to tRNA. The first experimental evidence …