The pETcoco expression vectors are designed to allow “on command” amplification of vector copy number from single copy (1–2 plasmid copies per cell) to medium copy (20– 50 per cell). The vector is maintained in the single copy state by utilizing the oriS and repE elements of the F episome together with the parABC partition determinants. The medium copy state is obtained by employing the RK-2 derived trfA replicator acting at oriV. The switch from single copy to medium copy status is achieved by inducing the expression of the trfA gene with arabinose. The dual replicon nature of these vectors promotes enhanced stability of recombinant plasmids and extremely low basal expression levels in the single copy state, while allowing robust target protein expression typical of the pET vectors. Unique restriction sites are shown on the circle map (below). The sequence is numbered relative to the start of T7 transcription at +1.
