Aminoacyl-tRNA Synthases Can Correct Acylation Errors

Aminoacyl-tRNA Synthases Can Correct Acylation Errors 

Many aminoacyl-tRNA synthases appear to contain a second catalytic site that serves to correct errors by hydrolyzing incorrectly matched amino acids and tRNAs. These proof-reading hydrolysis reactions are best understood in the case 

Identity elements in four tRNAs. Each circle represents one nucleotide. Filled circles indicate nucleotides that serve as recognition elements to the appropriate aminoacyl-tRNA synthase. It is possible that other identity elements occur in these structures that are still to be discovered. (From L. H. Schulman and J. Abelson, Recent excitement in understanding transfer RNA identity, Science 240 1591, June 17, 1988. Copyright 1988 by the AAAS. Reprinted by permission.) 

In this way the erroneous incorporation of valine in place of isoleucine is avoided. The sequential action of aminoacylation and proofreading sites contributes to an overall error frequency of translation of less than 1 in 10,000. 

Solvent-accessible surface representation of the GlnRS enzyme complexed with tRNA and ATP. The region of contact between tRNA and protein extends across one side of the entire enzyme surface and includes interactions from all four protein domains. The acceptor end of the tRNA and the ATP are seen in the bottom of the deep cleft. Protein is inserted between the 5 and 3 ends of the tRNA and disrupts the expected base pair between Ul and A72. (From M. G. Rould, J. J. Persona, D. Soil, and T. Steitz, Structure of E. coli glutamyl-tRNA synthetics complexed with tRNA ln and ATP at 2.8-A resolution, implications for tRNA discrimination, Science 246 1135-1142, 1989, 1989 by the AAAS.) 

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Synthases Attach Amino Acids to tRNAs Each Synthase Recognizes a Specific Amino Acid and Specific Regions on Its Cognate tRNA Aminoacyl-tRNA Synthases Can Correct Acylation Errors... 

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