title: Constitutive mutations in the controlling site region of the araBAD operon of Escherichia coli B/r that decrease sensitivity to catabolite repression.
abstract: Strains of Escherichia coli B/r containing a deletion of the regulatory gene araC are Ara-. Slow-growing revertants of these strains were isolated and designated aralc because they contain a second mutation in a controlling site, aral, that allows for a low level of constitutive expression of the araBAD operon (Englesbert et al., 1969). We mutagenized aralc delta C strains and selected mutants that grow faster in mineral L-arabinose medium. The new mutations, called araXc, map very close to the original aralc mutations and are in the controlling site region between araB and araC. The aralcXc delta C strains have a higher constitutive level of expression of the araBAD operon than the aralc delta C parents. The araXc mutations are cis acting and decrease the araBAD operon's sensitivity to catabolite repression. The araBAD operon is expressed equally well in ara delta C and ara C cya crp backgrounds. The repressor form of ara C protein is able to repress the constitutive synthesis due to the ara Xc allele.
mesh_terms: D001089:Arabinose / Q000378:metabolism*; D002238:Carbohydrate Epimerases / Q000378:metabolism; D002874:Chromosome Mapping; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism*; D005796:Genes; D005809:Genes, Regulator; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D009154:Mutation; D009876:Operon; D010770:Phosphotransferases / Q000378:metabolism
chemical_list: D001089:Arabinose; D010770:Phosphotransferases; D002238:Carbohydrate Epimerases; D005947:Glucose; D005990:Glycerol