The strong promoter of the tryptophan operon (Ptrp) gives high-level expression of recombinant proteins in E. coli. The inefficiency to control basal expression before induction is however a major obstacle towards the use of Ptrp, especially in the case of toxic proteins. To circumvent this problem, the Ptrp is regulated by the lacO operator placed downstream of the Ptrp promoter. In order to ensure a tight expression control, this biomodule also biomolodule encodes also for the lacIq protein under the control of mutated LacI promoter that enhances that expression of the LacI repressor resulting in strong repression of Ptrp unless the inducer IPTG is added. This system, originally published by De Lorenzo et al. (https://doi.org/10.1016/0378-1119(93)90533-9) ensures tight expression control during the lag phase and a robust expression following the addition of the inducer.

The Standard European Vector Architecture (SEVA) platform is a digital and physical repository for de-constructing and re-constructing complex prokaryotic phenotypes. SEVA provides a uniform syntax and vector architecture composed of preformatted arrangement of functional DNA modules: replication origins, antibiotic resistances and cargo modules. All plasmid modules were exchangeable and suitable for any Gram-negative host. SEVA is promoted and maintained by the Spanish National Centre for Biotechnology (CNB) in Spain. For more information, please visit SEVA home.