The gene coding for lipoprotein signal peptidase (lspA) and that for isoleucyl-tRNA synthetase (ileS) constitute a cotranscriptional unit in Escherichia coli.

The lspA gene coding for lipoprotein signal peptidase is located very close to the ileS gene coding for isoleucyl-tRNA synthetase on the Escherichia coli chromosome. Deletions were generated in vitro from both ends of the 4.3 kb fragment that carries the lspA gene and the ileS gene, and the expression of the two genes was examined before and after insertion of the trp promoter-operator at one end. The results indicate that the lspA and ileS genes constitute a cotranscriptional unit in the order of promoter- ileS - lspA . The gene order of dnaJ - rpsT - ileS - lspA - dapB around 0.5 min on the E. coli chromosome map was also determined.