Figure 1.

A diagram of the recombination between the pUNI entry vector and the pHOST to form a recombinant expression plasmid. The pUNI plasmid has an origin of replication from plasmid R6Kγ that requires use of a pir-containing strain of E. coli such as BW23474. The pUNI and pHOST plasmids are mixed with Cre-recombinase, incubated, and the mixture is transformed into a strain of E. coli that lacks pir. Selection for recombinants on kanamycin precludes replication of the unrecombined pHOST vector, and the use of E. coli TOP10 or DH5α guarantees that no unrecombined pUNI plasmids will form viable colonies. Recombination occurs in a directional manner at the loxP site, such that the gene follows the promoter and fusion protein in the recombinant expression plasmid. This figure is modifed from Liu et al. 2000.