Chapter 15 Notes

Chapter 15 Notes - Lac Operon: Inducible Operon; repressor...

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Unformatted text preview: Lac Operon: Inducible Operon; repressor is normally active 3 enzymes: beta-galactosidase, permease, transacetylase Transcription of the lactose Operon is controlled by 2 regulatory proteins. The CAP can bind to CAP binding site and facilitate transcription. The lac repressor protein can bind to operator site and block transcription. The CAP can bind to binding site only if cAMP is bound to it. When only glucose is present: concentration of cAMP is low, so RNA polymerase cannot bind efficiently to the promoter and transcription does not occur unless the catabolite binding protein is bound to the activator binding site. Therefore, transcription of lac Operon does NOT occur in the presence of glucose. When both glucose and lactose are present : there is insufficient cAMP to bind to CAP, which cannot bind to CAP binding site; without the cAMP & CAP complex, RNA polymerase cannot bind to promoter and initiate transcription, even though lactose binds to repressor and prevents it from binding to operator...
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Chapter 15 Notes - Lac Operon: Inducible Operon; repressor...

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