Optimized promoter–operator element consisting of phage T5 promoter (recognized
by the E. coli RNA polymerase) and two lac operator sequences which increase lac
repressor binding and ensure efficient repression of the powerful T5 promoter
• Synthetic ribosomal binding site, RBSII, for high translation rates
• 6xHis-tag coding sequence either 5' or 3' to the cloning region
• Multiple cloning site and translational stop codons in all reading frames for convenient
preparation of expression constructs
• Two strong transcriptional terminators: t0 from phage lambda (Schwarz et al. 1987),
and T1 from the rrnB operon of E. coli, to prevent read-through transcription and
ensure stability of the expression construct
• β-lactamase gene (bla) conferring resistance to ampicillin (Sutcliffe 1979) at 100 μg/ml.
The chloramphenicol acetyl transferase gene (CAT) present between t0 and T1 has no
promoter and is not normally expressed.* Depending on the bacterial strain and insert,
low CAT activities may be detectable.
• ColE1 origin of replication (Sutcliffe 1979)*
Restriction maps and sequences for the cloning regions of QIAexpress vectors are
presented in the appendix on page 117. The entire sequence information is available at