tRNA Identity

Abstract

In the translation of genetic information from nucleic acid to protein, transfer RNA plays a crucial intermediate role. Each codon is read by a unique tRNA, which has been aminoacylated with the appropriate amino acid. Because of degeneracy in the genetic code there are, in general, more than one tRNA for each amino acid (1). Although there are some exceptions, there is a single aminoacyl tRNA synthetase (AAS) for cach amino acid. An AAS must correctly recognize and activate an amino acid and then join it to each of the cognate set of tRNAs. By virtue of the fact that they must function interchangeably on the ribosome during protein synthesis, all tRNAs have similar primary (2), secondary (3), and tertiary (4, 5) structures (Figure 1). Within these constraints each cognate set of tRNAs contains distinct elements that mediate correct recognition by the AAS. These elements comprise the identity of a tRNA. Identity elements can be both positive and negative. Positive elements are those features of the tRNA that the cognate AAS recognizes directly, and negative elements are those features that block the recognition by other AASs.