Role of the regulator-gene product (repressor) in catabolite repression of beta-galactosidase synthesis in Escherichia coli.
1. The specific role of the lac repressor (i-gene product) in transient catabolite repression evoked by the introduction of glucose into the medium has been investigated in Escherichia coli by using mutants of the i-gene. 2. A temperature-sensitive mutant (i(TL)) is normally inducible and demonstrates transient repression when grown at 32 degrees . At 42 degrees it is about 20% constitutive and transient catabolite repression is abolished. 3. A strain carrying an amber suppressor-sensitive mutation in the i-gene is phenotypically constitutive and also fails to show transient catabolite repression. 4. Insertion of Flaci(+) into this strain restores both inducibility and transient repression. 5. It is concluded that the i-gene product interacts with the catabolite co-repressor in such a way that its affinity for the operator is increased.
D004790:Enzyme Induction; D004794:Enzyme Repression; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology*; D005696:Galactosidases / Q000096:biosynthesis*; D005809:Genes, Regulator; D005827:Genetics, Microbial; D005947:Glucose / Q000378:metabolism; D006027:Glycosides / Q000494:pharmacology; D009154:Mutation; D013696:Temperature
D006027:Glycosides; D005696:Galactosidases; D005947:Glucose