A group of adjacent and coordinately controlled genes for lactose metabolism in E. coli, chiefly famous because it was the first example of this type of gene regulation. The operator region of the operon has a lactose repressor, a tetrameric protein (subunits 360 aa), bound until lactose becomes available in the medium. Allolactose, formed by transglycosylation within the cell, binds to the repressor protein and inhibits its interaction with the operator region, lifting the block to transcription of the suite of genes required for lactose metabolism and uptake. LacZ codes for β-galactosidase, lacY for the lactose carrier protein (permease), lacA for the transacetylase.
Subjects: Medicine and Health.