Molecular cloning and characterization of the purE operon of Escherichia coli

The purE operon of Escherichia coli has been cloned and localized to a 1.7-kb HpaI fragment. The operon has been further characterized by subcloning into the lac fusion vector, pMC1403, and by the construction of BAL 31-generated deletions. The purE regulation region has been identified by assay of beta-galactosidase produced by pur-lac fusion plasmids and by RNA polymerase binding to end-labelled restriction fragments. Two purE promoters have been identified; one strong that is regulated by purines, the other weaker which is not regulated. The latter may be internal to the purE1 structural gene.