How can I express toxic protein in E. coli?
FAQ ID -373

To reduce the effects of protein toxicity on bacterial cell growth prior to induction, the level of basal transcription that occurs in the absence of induction (“leakiness”) should be repressed as much as possible, and the number of generations before induction should be kept to a minimum.

For very toxic proteins, we recommend using the pQE-80L series of expression vectors in the M15[pREP4] E. coli host strain. The pQE-80L vectors have a cis-lacIq gene that overexpresses the lac repressor, in addition to a lacI repressor gene present in trans on a separate pREP4 plasmid. This combination of two repressor modules results in highly efficient suppression of recombinant protein expression prior to induction and gives the best chance of successful expression of toxic proteins. Furthermore, induction of the toxic protein should be done at a time point as late as possible, and the IPTG concentration used for induction should be reduced. Conditions have to be optimized for each application.

Another alternative is to use cell-free protein biosynthesis systems , like the EasyXpress Protein Synthesis Kit. The advantages of cell-free expression systems include time savings, the possibility to produce proteins that are toxic and the ability to adapt reaction conditions to the requirements of the synthesized protein.