T7 Expression Systems for Inducible Production of Proteins from Cloned Genes in E. coli

Inducible T7 expression systems are capable of producing a wide range of proteins in E. coli. Improvements over common practice include: (1) preventing unintended induction by establishing and maintaining expression strains in non-inducing growth media composed entirely of purified components instead of complex growth media that may variably induce target proteins on approach to saturation; and (2) expressing many target proteins in parallel by convenient and productive auto-induction in BL21(DE3) and other suitable hosts, instead of IPTG induction. From the earliest days, basal expression prevented establishment of inducible strains for producing proteins that are stressful to the host. Newly developed pAL vectors now reduce basal expression to levels where coding sequences for even the most stressful proteins can be maintained and induced. Asymmetric ligation allows simple and efficient cloning of individual coding sequences or simultaneous cloning of two or three coding sequences for co-expression from a single pAL vector. © 2018 by John Wiley & Sons, Inc.