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The lactose operon (lac operon) is an operon required for the transport and metabolism of lactose in E. coli and many other enteric bacteria.Although glucose is the preferred carbon source for most enteric bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available through the activity of β-galactosidase. [1]
The LacY gene is a component of the lac operon that encodes lactose permease, a protein responsible for breaking down lactose into glucose and galactose, alongside transacetylase and beta galactosidase. The absence of lactose permease leads to the inability of lactose to enter the cell for further metabolic processes.
English: 1: RNA Polymerase, 2: Repressor, 3: Promoter, 4: Operator, 5: Lactose, 6: lacZ, 7: lacY, 8: lacA. Top: The gene is essentially turned off. There is no lactose to inhibit the repressor, so the repressor binds to the operator, which obstructs the RNA polymerase from binding to the promoter and making lactase. Bottom: The gene is turned on.
The lac operon of the model bacterium Escherichia coli was the first operon to be discovered and provides a typical example of operon function. It consists of three adjacent structural genes, a promoter, a terminator, and an operator. The lac operon is regulated by several factors including the availability of glucose and lactose.
The presence of allolactose, a metabolic product of lactose, is sensed through the activity of the lac repressor, which inhibits transcription of the lac operon until lactose is present. Thus, if glucose is present, cAMP levels remain low, so CAP is unable to activate transcription of the lac operon, regardless of the presence or absence of ...
Galactoside permease is a protein coded by the lacY gene of the lac operon, and is found bound to the membrane of a cell for the purpose of binding galactoside molecules that have been solubilized. The protein is part of a system whose main function is to catalyze the accumulation and transport of lactose and other beta-galactosides across the ...
lac operon · opéron lactose english français transcription factors ... This diagram uses embedded text that can be easily translated using a text editor.
The lacZYA operon houses genes encoding proteins needed for lactose breakdown. [2] The lacI gene codes for a protein called "the repressor" or "the lac repressor", which functions to repressor of the lac operon. [2] The gene lacI is situated immediately upstream of lacZYA but is transcribed from a lacI promoter. [2]