LEC09.ppt [Compatibility Mode]

LEC09.ppt [Compatibility Mode] - Announcements...

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Unformatted text preview: Announcements Announcements Review next week in class Wed ! Review next week in class- Wed ! Midterm 5-7 pm- Thursday ! Quiz 2: everyone will get 0.5 pts additiona additional ! Quiz 3: this weekend lac operon is also under positive control Observation: Lactose media : !-gal activity high Glucose media: !-gal activity low Glu+lac media: !-gal activity low lac repressor is not binding to operator and yet !-gal is not being expressed Lac operon Lac operon ! Combination of negative and positive control ! lac repressor acts as a negative regulator by turning off transcription ! CAP-cAMP complex acts as a positive regulator by turning on expression regulator by turning on expression ! Both regulatory proteins are under allosteric control Many operons are under general control referred to as catabolite repression Glucose metabolism is favored over lactose metabolism (or any other lactose metabolism (or any other disaccharide) Level of glucose in media is detected by cAMP glucose cAMP glucose cAMP CAP ( CAP ( C atabolite atabolite A ctivator ctivator P rotein) rotein) aka CRP ( aka CRP ( c AMP AMP r eceptor eceptor p rotein) rotein) ! CAP-cAMP binds to CAP cAMP binds to specific DNA sequences ! Binding results in a bend in the DNA ! CAP-cAMP also interacts directly with interacts directly with RNA polymerase to stimulate binding to weak promoter sequences X-ray structure: " CTD - CAP•cAMP - DNA " CTD CAP-cAMP Activation by increasing binding...
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LEC09.ppt [Compatibility Mode] - Announcements...

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