The cloning and analysis of the aroD gene of E. coli K-12

A 5.6-kb PstI fragment containing the structural gene (aroD) for 5-dehydroquinate hydrolyase (DHQase) of Escherichia coli K-12 has been cloned into recombinant plasmid pJKK12. The bacterial fragment contains two Bg/II, one HpaII, one SalI and one XhoI site, but no EcoRI, HindIII or BamHI sites. the DHQase activity extracted from strains harboring pJKK12 had properties identical to those of the enzyme isolated from wild-type E. coli. The native protein appears to be a dimer composed of two 31 500 dalton subunits. aroD6 strains transformed with pJKK12 had an 11-fold and 34-fold increase in activity compared to untransformed wild-type controls grown on L broth and minimal medium, respectively. No increase of dehydroquinase activity was found in polynucleotide phosphorylase deficient strains of E. coli. At least four constitutively expressed genes are encoded on the fragment.