Transfer RNA recognition by aminoacyl-tRNA synthetases

The aminoacyl-rRNA synthetases are an ancient group of enzymes that catalyz e the covalent attachment of an amino acid to its cognate transfer RNA, The question of specificity that is, how each synthetase selects the correct i ndividual or isoacceptor set of tRNAs Sor each amino acid has been referred to as the second genetic code.:A wealth of structural, biochemical, and ge netic data on this subject has accumulated over the past 40 ears. Although there are now crystal structures of sixteen of the twenty synthetases from various species, there ai-e only a Sew high resolution structures of synthe tases complexed with cognate tRNAs. Here we review briefly the structural i nformation available for synthetases, and focus on the structural features of tRNA that may be used for recognition. Finally, we explore in detail; th e insights into specific recognition gained from classical and atomic group mutagenesis experiments performed with tRNAs, tRNA fragments, and small RN As mimicking portions of rRNAs. (C) 2000 John Wiley & Sons, Inc.