cis-Repressed pQE Kan Vector Set

From QIAGEN, this vector set is designed for cis-repressed high-level expression of N-terminally 6xHis-tagged proteins in E. coli. The vectors are similar to those in the N-Terminus pQE Vector Set but additionally express the lacI^q gene product, which represses protein expression prior to IPTG induction, eliminating the need to include this gene on another plasmid. The set is recommended for expressing gene products toxic to E. coli.

The set provides vectors with a kanamycin resistance gene alongside an ampicillin resistance gene, enabling selection by either antibiotic. These are in vivo expression vectors with an N-terminal 6xHis tag, no tag removal sequence, and all three reading frames provided. In-frame cloning is necessary.

Once a DNA insert is incorporated, the vector is transformed into E. coli cells and protein expression is induced by the addition of IPTG. After cell lysis, 6xHis-tagged proteins can be purified by Ni-NTA affinity chromatography under native or denaturing conditions. The cis-repression feature reduces basal (leaky) expression, supporting cloning and expression of proteins that are toxic or unstable when expressed constitutively, and is compatible with standard pQE expression workflows in E. coli.