Overproduction of theBacillus subtilisglutamyl-tRNA synthetase in its host and its toxicity toEscherichia coli

Abstract

The Bacillus subtilis glutamyl-tRNA synthetase (GluRS), encoded by the gltX gene, aminoacylates its homologous tRNA^Gluand tRNA^Glnwith glutamate. This gene was cloned with its sigma^Apromoter and a downstream region including a rho-independent terminator in the shuttle vector pRB394 for Escherichia coli and B. subtilis. Transformation of B. subtilis with this recombinant plasmid (pMP411) led to a 30-fold increase of glutamyl-tRNA synthetase specific activity in crude extracts. Transformation of E. coli with this plasmid gave no recombinants, but transformation with plasmids bearing an altered gltX was successful. These results indicate that the presence of B. subtilis glutamyl-tRNA synthetase is lethal for E. coli, probably because this enzyme glutamylates tRNA₁^Glnin vivo as it does in vitro.Key words: glutamyl-tRNA synthetase overproduction, Bacillus subtilis, toxicity, Escherichia coli.