Expression of a bacterial gene for guanine synthesis inserted into colicin E1 factor by an in vitro recombination

Expression of prokaryotic genes inserted into ColE1 and pVH51 plasmids

One of the DNA fragments obtained from EcoRI digests of guaA-transducing lambda phage DNA contains the intact bacterial guaA gene at its one end and the lambda phage R gene at the other end. This DNA fragment, named coslambda-guaA, does not contain promoter-operator regions of the gua operon and of the lambda phage R gene, coslambda-guaA DNA fragments were inserted in two different orientations into respective DNAs of EcoRI-cleaved ColE1 and pVH151 (= mini ColE1). Mitomycin C stimulated the guaA enzyme production in the cells harboring the hybrid plasmids with one coslambda-guaA DNA fragment insertion orientation (orientation I), but not the other (orientation II). The lambda-endolysin, product of the lambda phage R gene, was induced by mitomycin C treatment in orientation II, but it was not detected in orientation I. These results suggest that both ColE1 and pVH51 DNAs contain the mitomycin C-responsive promoter which allows transcription of the genes connected with these DNAs.

Isolation and characterization of a mutant ColE1 plasmid that allows constitutive colicin E1 synthesis

It has been possible to isolate a ColE1 mutant which synthesizes colicin E1 constitutively. This result shows that there must be a gene(s) responsible for the regulation of colicin E1 synthesis.