Bacterial Gene Regulation Flashcards
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
What inhibits adenylate cyclase?
-active transport of glucose into the cell
What happens when cAMP binds to the CPR protein?
-activated transcription
-The lactose utilization genes are only one of the many sets of genes that can be activated by CPR.
-absence of glucose, presents of lactose
-look at notes
When are lactose genes ecpressed?
-glucose is absent
-lactose is present
-look at notes
2-Component Regulatory Systems
-a signaling pathway commonly found in bacteria that allows them to respond to changes in their environment
-The signal is transmitted by phosphorylation/dephosphorylation of the response regulator by the sensor kinase
-look at notes
What is component #1 in the regulatory system?
-a sensory kinase protein that receives a signal, often extracellular, and transmits that signal to component #2
What is component #2 in the regulatory system?
-is a response regulator that is usually a transcription regulator (a repressor or activator)
2-Component Regulatory Systems in Bacteria
-Many bacterial species have 20-40 different 2-component systems encoded in their genomes
-Ex. Pho regulation = inorganic phosphate
-Porin regulation = osmotic pressure
Sporulation
-Spore formation requires the cooperative action of two cells, the mother cell and the developing forespore.
-Each cell must change its pattern of gene expression several times during the sporulation process, and these changes must happen in proper order.
-The two cells communicate to activate new sigma factors to direct transcription at the proper time and in the proper cell type
What does the forespore make?
-internal spore components
What does the mother cell make?
-external spore wall and coat components
How does sporulation work?
-signal from endospore activates sigma E, transcription of early endospore genes
-Then signal from mother cell triggers synthesis of sigma G in endospore and pro-sigma K in mother cell
-Lastly, signal from endospore activates sigma K.
-Look at notes
What is Quorum Sensing?
-A mechanism for a population of bacterial cells to determine their population density and respond accordingly.
-some activates are only useful at high or low concentration
What do all cells in the population of quorum sensing produce?
-a small molecule “Autoinducer” that is released from the cell
How does Quorum Sensing work?
-Cells contain a regulatory protein (repressor or activator) that can bind the autoinducer ONLY when it is a high concentration
-Gene regulation is turned on or off at low or high cell density
-Look at notes
What do various species use to regulate?
-Luminescence (light production), virulence, biofilm formation, transformation (DNA uptake), sporulation, and antibiotic synthesis
What do Gram Pos use?
-peptides
-8-11 amino acids
