Bacterial Gene Regulation Flashcards
(40 cards)
DNA binding proteins
-Do the regulating
-Domain containing protein-protein contacts, holding protein dimer together (2 subunit)
-DNA-binding domain fits in major groove and along sugar-phosphate backbone.
-look at notes
Transcriptional Control
-repressors exert NEGATIVE control
-look at notes
Arginine graph
-cell number and total protein are positive increasing lines
-when arginine is added its line goes from increasing positive to flatting out
-arginine production repressed
Lactose graph
-cell number and total protein are increasing lines
-when lactose is added, it removes the repressor, and B-Galacto-sidase increases
How do the Arg (arginine) repressors act when it binds the “corepressor” arginine?
-transcription is blocked
How does the Arg (arginine) repressors act when the “corepressor” does not bind to arginine?
-Transcription proceeds
Can arg operator be placed in front of arg promoters and work?
-No, because it is to far upstream
What happens to the Lac repressor when a repressor binds to the lac operator with no inducer?
-Transcription blocked
What happens when an inducer binds to the Lac Repressor?
-The inducer pulls the Lac repressor off the lac operator and transcription proceeds
Repressors
-bind to sites in the DNA called “operators”
-Prevent transcription by blocking access of RNA polymerase to the promoter (steric hindrance)
-Often are turned on or off by the binding of a small molecule
What sites of the promoter do they overlap on?
-They overlap on the -35, -10 or +1 site
What are considered small molecules?
-corepressors
-inducer
-effector
What do activators exert?
-Positive control
-look at notes
What happens when an RNA polymerase binds weakly to a mal promoter with an activator binding site?
-The maltose activator protein doesn’t bind
-No transcription
What happens when the maltose activator binds to the activator binding site?
-An inducer (maltose) binds)
-The RNA polymerase binds strongly
-Transcription proceeds
Where can activators bind?
-near or far upstream of the promoter
-look at notes
Can repressor bind far upstream of the promoter?
-No
Activators
-bind to sites in the DNA called “Activator-Binding Sites”
-Activate transcription by a positive interaction with RNA polymerase binding at the promoter.
-Often are turned on or off by the binding of a small molecule “effector”
Do activators over lap?
-Activators DON’T overlap
Can the activator and RNAP polymerase bind at the same time?
-Yes
Can E. Coil use many carbon sources?
-Yes
Catabolite Repression in E. Coli
-E. Coli will use ONLY glucose until glucose is exhausted
-Once glucose is exhausted E. Coli will induce lactose utilization genes
-Same for other secondary carbon sources
Catabolite Repression Graph
-positive increasing glucose line, then glucose exhausted to line flattens, then lactose and line is positively increasing but not as steep as glucose
-more B-Galactosidase with lactose
Production of cyclic AMP (cAMP)
-Active transport of glucose into the cell inhibits the enzyme adenylate cyclase.
-A lack of glucose results in production of cAMP
-cAMP is the signal that the cell lacks glucose
