EXAM 3 P4 Flashcards
DNA binding proteins
carry out transcription
majority function as dimers
most recognize sites in DNA known as inverted repeats. recognize sequences next to and facing each other
specificity
repressors
exert negative control
when bound to DNA, they turn the gene off, blocking RNAP access to the promoter
locate the operator
example of repression
arginine synthesis
once a lot is present, no more needs to be made so expression of the arginine synthesis enzyme is turned off
induction
exerts positive control
when lac is dumped into the growth medium, cells turn on expression of the lac utilization gene
arg repressor
acts when it binds to the corepressor of arginine
this allows the repressor to be active and bind to the operator sequence of DNA
this blocks RNAP from effectively using the promoter, preventing transcription
lac repressor
binds to the DNA operator, shutting lac genes off
when the corepressor is added, it binds to the repressor, unbinding it from the DNA. polymerase can now carry out transcription
inducer
small lac molecule
turns gene expression on
causes the repressor to stop binding
corepressor
turn gene expression off causing the repressor to start binding
activators
exert positive control
bind next to promoters to increase transcription
catabolite repression
glucose grows and becomes exhausted, so lactose growth begins
true for all carbon sources
production of cAMP
adenine cyclase enzyme cyclizes phosphate to create cAMP from ATP
what is cAMP (cyclic AMP)
an internal signaling molecule for lack of glucose.
as long as glucose is present, cAMP is inhibited
if glucose runs out, cAMP is produced by adenine cyclase
cAMP and CRP
cAMP binds to CRP protein and activates transcription
CRP (catabolite repression protein)
alone it does nothing, but when cAMP is produced, CRP binds and dimerizes, becoming a functional DNA binding protein.
binds to an activator binding site upstream of promoter
CRP is an activator
component 1
a protein called a sensor kinase. it senses an environmental signal (change in temp, pH) and transmits this information to the other protein
component 2
response regulator
usually a transcription regulator, so the protein is a repressor or an activator. takes the info from comp 1 and decides what response to take
what is the signal transmitted in 2 component regulatory system
phosphorylation or dephosphorylation
takes phosphate from ATP and sticks it to itself. then puts it onto the response regulator. a phosphorylated regulator becomes active
spores
the most resistant lifeform on earth
formation requires a large mother cell and a small fore spore
sporulation
sigma factor becomes active only in the fore spore. a signal is sent to the mother, activating sigma in the mother spore. the fore spore produces the spore, and the mother cell produces the spores components, but eventually dies
mother spores
focus on the outer layers to protect the spore from chemicals
eventually die
quorum sensing
allows single celled organisms to function as a population in a coordinated fashion.
can decide when to turn on a specific gene at a certain time
regulates many things like luminescence and biofilm formation
autoinducer
small molecule associated with quorum sensing