An analysis of enzymes that load amino acids onto transfer RNAs—an operation at the heart of protein translation—offers new insights into the evolutionary origins of the modern genetic code, researchers report. Their findings appear in the journal PLOS ONE.
The researchers focused on aminoacyl tRNA synthetases, enzymes that "read" the genetic information embedded in transfer RNA molecules and attach the appropriate amino acids to those tRNAs. Once a tRNA is charged with its amino acid, it carries it to the ribosome, a cellular "workbench" on which proteins are assembled, one amino acid at a time.
Synthetases charge the amino acids with high-energy chemical bonds that speed the later formation of new peptide (protein) bonds. Synthetases also have powerful editing capabilities; if the wrong amino acid is added to a tRNA, the enzyme quickly dissolves the bond.
"Synthetases are key interpreters and arbitrators of how nucleic-acid information translates into amino-acid information," said Gustavo Caetano-Anollés, a University of Illinois professor of crop sciences and of bioinformatics. Caetano-Anollés, who led the research, also is a professor in the U. of I. Institute for Genomic Biology. "Their editing capabilities are about 100-fold more rigorous than the proofreading and recognition that occurs in the ribosome. Consequently, synthetases are responsible for establishing the rules of the genetic code."