The repression of the lac operon in the absence of lactose can be improved through DNA looping, in which LacI binds to O 1 and a second operator sequence, either O 2 or O 3. This increases the local ...
The operon is regulated by Lac repressor, the product of the lacI gene, which is transcribed from its own promoter (PI). The repressor inhibits transcription by binding to the lac operator (O).
For example, repression of the lac operon by its repressor, called lacI, is inhibited by the ligand allolactose, to which the repressor protein directly binds. Thus, lactose, from which ...