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 (iTL) is normally inducible and demonstrates transient repression when grown at 32°. At 42° 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.
The role of the regulator-gene product (repressor) in catabolite repression of β-galactosidase synthesis in Escherichia coli
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J. Palmer, V. Moses; The role of the regulator-gene product (repressor) in catabolite repression of β-galactosidase synthesis in Escherichia coli. Biochem J 1 January 1968; 106 (2): 339–343. doi: https://doi.org/10.1042/bj1060339
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