A single base substitution in the variable pocket of yeast tRNA Arg eliminates species-specific aminoacylation

Abstract

Early biochemical data showed that aminoacyl-tRNA synthetases often displayed species-specific recognition of tRNA. We compared the ability of purified Saccharomyces cerevisiae and Escherichia coli arginyl-tRNA synthetases to aminoacylate native and transcribed yeast tRNA Arg as well as E. coli tRNA Arg. The kinetic data revealed that yeast ArgRS could charge E. coli tRNA Arg, but at a lower efficiency than it charged either the transcribed or native yeast tRNA Arg. E. coli ArgRS can acylate only its cognate E. coli tRNA. Strikingly, a single base change from C to A at position 20 in yeast tRNA 3 Arg altered the species specificity. The transcript of yeast tRNA 3 ArgCA20 mutant was aminoacylated by E. coli ArgRS with a 10 6 increase in k cat/ K m over that for aminoacylation of yeast tRNA 3 Arg transcript. This indicates that A20 is not only an important identity of E. coli tRNA Arg, but is also the key to altering species-specific aminoacylation of yeast tRNA Arg.