N-Terminus pQE Vector Set

Designed for high-level expression of N-terminally His-tagged proteins, the QIAGEN N-Terminus pQE Vector Set comprises the vectors pQE-9, pQE-30, pQE-31, pQE-32, and pQE-40. The vectors pQE-30, pQE-31, and pQE-32 provide the multiple cloning site in all three reading frames, while pQE-9 carries an alternative, shorter multiple cloning site. The pQE-40 vector is intended for DHFR-fusion proteins and is recommended for expression of poorly expressed proteins or short peptides prone to proteolysis, as DHFR enhances both stability and antigenicity. Because DHFR is poorly immunogenic in mouse and rat, DHFR-fusion proteins are suited to epitope screening.

Each vector carries an optimized promoter/operator element consisting of the phage T5 promoter and two lac operator sequences, a synthetic ribosomal binding site (RBSII) for efficient translation, a 6xHis-tag coding sequence positioned 5' or 3' to the polylinker, translational stop codons in all reading frames, and two strong transcriptional terminators (t0 from phage lambda and T1 from the rrnB operon of E. coli). The ColE1 origin of replication is derived from pBR322, and the beta-lactamase (bla) gene confers ampicillin resistance. Expression is induced by addition of IPTG. The pQE-TriSystem constructs can also serve as a shuttle vector for protein expression in insect cells or be transfected into mammalian cells.

Specifications include in vivo expression, an N-terminal 6xHis tag, E. coli as the expression host, no tag removal sequence, a requirement for in-frame cloning, and provision of all three reading frames. Vectors can be maintained in any E. coli strain that is ampicillin-sensitive and carries the pREP4 repressor plasmid, or harbors the lacIq gene on the F-factor episome.