The role of the catalytic domain of E. coli GluRS in tRNAGln discrimination.

Discrimination of tRNA(Gln) is an integral function of several bacterial glutamyl-tRNA synthetases (GluRS). The origin of the discrimination is thought to arise from unfavorable interactions between tRNA(Gln) and the anticodon-binding domain of GluRS. From experiments on an anticodon-binding domain truncated Escherichia coli (E. coli) GluRS (catalytic domain) and a chimeric protein, constructed from the catalytic domain of E. coli GluRS and the anticodon-binding domain of E. coli glutaminyl-tRNA synthetase (GlnRS), we show that both proteins discriminate against E. coli tRNA(Gln). Our results demonstrate that in addition to the anticodon-binding domain, tRNA(Gln) discriminatory elements may be present in the catalytic domain in E. coli GluRS as well.