title: Regulation of expression of the uxu operon and of the uxuR regulatory gene in Escherichia coli K12.
abstract: Gene fusions between the lac structural genes and various genes of the hexuronate system of Escherichia coli K12 were isolated by the technique of Casadaban. Mud(Aprlac) and lambda plac-Mu insertion mutants were constructed in which the lac genes were fused to the regulatory region of the uxu operon. In all the uxu-lac fusion strains, beta-galactosidase expression was shown to be inducible by the natural inducers of the uxu operon (glucuronate and fructuronate) and sensitive to catabolite repression by glucose. In addition we isolated a Mud(Aprlac) fusion where the lac genes were fused to the uxuR regulatory gene. In this fusion the synthesis of beta-galactosidase reflects the regulation of the uxuR gene. In the presence of a wild-type uxuR allele, partial repression of beta-galactosidase expression was found; the repression was removed when inducer was added. This result indicates that while the uxuR gene is subject to autogenous control, the uxuR repressor may have only a low affinity for its own operator.
mesh_terms: D003090:Coliphages / Q000235:genetics; D004790:Enzyme Induction; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005786:Gene Expression Regulation; D005796:Genes; D005798:Genes, Bacterial; D005809:Genes, Regulator; D005965:Glucuronates / Q000235:genetics; D020723:Glucuronic Acid; D006603:Hexuronic Acids / Q000235:genetics; D007763:Lac Operon; D009154:Mutation; D009876:Operon; D001616:beta-Galactosidase / Q000096:biosynthesis
chemical_list: D005965:Glucuronates; D006603:Hexuronic Acids; D020723:Glucuronic Acid; D001616:beta-Galactosidase