Aminoacyl-tRNA synthetases are multidomain proteins responsible for the attachment of specific amino acids to their tRNA substrates. Prolyl-tRNA synthetases (ProRSs) are notable due to their particularly diverse architectures through evolution. For example, Saccharomycese cerevisiae ProRS possesses an N-terminal extension with weak homology to a bacterial-specific domain typically present as an insertion (INS) within the aminoacylation active site. The INS domain has been shown to contain a "post-transfer" editing active site responsible for cleaving the aminoacylester bond of misacylated Ala-tRNA Pro species. However, wild-type S. cerevisiae ProRS does not perform posttransfer editing in vitro. Here, we show that replacement of the N-terminal domain of S. cerevisiae ProRS with the Escherichia coli INS domain confers posttransfer editing function to this chimeric enzyme, with specificity for yeast Ala-tRNAPro. In contrast, the isolated IMS domain displays only weak editing activity and lacks tRNA sequence specificity. These results emphasize the modular nature of synthetase editing active sites and demonstrate how in evolution, a weak editing activity can be converted to a more robust state through fusion to the body of a synthetase. In this manner, a single editing module can be distributed to different synthetases, and simultaneously acquire specificity and enhanced activity.
|Original language||English (US)|
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Feb 13 2007|
- Prolyl-tRNA synthetase
- Saccharomyces cerevisiae