BIOL 102 Lecture Notes - Lecture 12: Transcription Factor Ii D, Lac Repressor, Lactose Permease
7 Dec 2016
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Lactose metabolism in e. coli [example of gene regulation] Lac ------------ glu + gal: b-galactosidase. When grown on lactose: much beta-galactosidase: lots of galactose permease bringing glucose through walls. Jacob and monod: described the first operon: the lac operon. Gene system that regulates lactose metabolism: studied enzyme adaptation (appears only when the cell has been exposed to the substrate for that enzyme, discovered the lac repressor. When lactose is absent from the environment, allolactose is not made and the lac repressor is free to bind to the lac operator, inhibiting the transcription of the operon. Lac repressor binds to the operator and inhibits transcription lacp rna polymerase binding site (lac promoter: restricts the transcription. Lactose present, a small amount of isomerizes to allolactose, an isomer of lactose. Allolactose binds the repressor protein, causes conformational change and no longer binds to the operator.
