tRNA synthetase is an enzyme that attaches the appropriate amino acid onto its tRNA. It does so by catalyzing the esterification of a specific cognate amino acid or its precursor to one of all its compatible cognate tRNAs to form an aminoacyl-tRNA. Once the tRNA is charged, a ribosome can transfer the amino acid from the tRNA onto a growing peptide, according to the genetic code. Aminoacyl tRNA therefore plays an important role in DNA translation, the expression of genes to create proteins.
Synthetases in mammalian cells are now known to have expanded functions, including activities in signal transduction pathways. Cell surface receptors for secreted forms and interacting partners in the nucleus are being identified and investigated from the standpoint of structure-function relationships, and understanding the evolutionary forces that introduced new motifs and activities in tRNA synthetases. These activities offer the opportunity to understand the mechanistic side of expanded functions to the point where therapeutic applications can be envisioned.