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."