A versatile vector for controlled expression of genes in Escherichia coli and Salmonella typhimurium.

We have constructed two expression vectors based on the pJF118HE vector developed for Escherichia coli by Fürste et al. [Gene 48 (1986) 119-131]. The tac promoter (ptac) was exchanged for the trc promoter (ptrc) and an NdeI site was created at the appropriate distance from the ribosome-binding site. The NdeI site permits cloning of a gene at its translation start point without altering the amino-acid sequence of the synthesized protein, while ptrc and the lacIQ gene confer inducible and controlable expression. We have tested these plasmids in E. coli and Salmonella typhimurium.