4-3: Transcriptional Regulation Flashcards
What is regulation
Controlling the abundance/activity of gene products
How cells adapt to environment
How is transcription initiation regulated
Control whether or not RNAP binds a promotor and transcribes (or the rate at which this occurs)
What protein largely regulates intiation
Transcription factors
What is sensing
Know which genes to turn off/on based on cues from envrionment
Most regulatory proteins are…
DNA-binding proteins
DNA-binding proteins must have what kind of domain… e.g.?
DNA-binding domains
Helix-turn-helix
What is recognized by DNA binding proteins
Consensus sequence
Transcription factors that promote transcription are…
Activators (bind DNA at promotor & recruit RNAP) “positive control”
Transcription factors than inhibit transcription are…
Repressors (bind DNA and prevent RNAP from binding, or prevents initation once bound) “negative control”
What is the sequence bound by the repressor called
Operator (after promotor region)
How is transcription regulated allosterically
Molecule binds activator or repressor to activate it
What are inducers
“Turn on” activator proteins (or inactivate repressors)
What are corepressors
Activate repressor proteins
What is an inducible system
System that is off by default, can be turned on
What is a repressible system
One that is on by default, can be turned off
What is a repressor protein that controls the expression of arginine biosynthesis operon
ArgR
How does ArgR function in low and high arginine levels
Low = not bound by arginine, does not bind DNA, transcription of arginine proceeds
High = arginine binds ArgR. so it binds the operator and prevents transcription
The machinery for breaking down lactose is encoded by the…
Lac operon
What is the repressor of lac operon
LacI repressor protein
What does LacI do when lactose is available vs absent
Available = lactose isomer (allolactase = inducer) binds LacI and inactivates it
Absent = LacI binds lac operator preventing transcription of lac operon (because it would make machinery for lactose breakdown; there is none present = wasted energy)
What happens to the lac operon in the presence of glucose
cAMP production inhibited
Lac operon requires CRP (cAMP receptor protein) to bind cAMP. Together they would bind the promotor region & recruit RNAP
What does the Lac operon require
Lactose and low glucose levels
cAMP is a…
Signaling molecule/second messenger
What is a signaling molecule
Produced in response to a signal, regulate processes in cell
What is ppGpp
Signaling molecule produced in response to aa starvation. Shuts down protein synthesis and induces aa biosynthesis
What is quorum sensing
Chemical communication: sensing local density of cells through secretion/detection of specific molecules
Why is quorum sensing important
Coordinate group behaviours like biolfilm formation, virulence
What are the molecules secreted in quorum sensing. How do they work
Autoinducers
Only accumulate at high density = group
Name an autoinducer
Acyl homoserine lactones (AHL)
What are the proteins used in two-component regulatory system
Sensor kinase
Response regulator
What is sensor kinase
Cytoplasmic membrane protein. Senses signals that activate kinase. Add P to response regulator
What is the response regulator
Active once phosphorylated by sensor kinase. Binds DNA to regulate expression of genes (activate/repress)
What is a local vs global regulator
Local regulator = control expression of limited number of genes
Global regulator = regulate large numbers of different genes in response to signal
Complete set of genes controlled by a given regulator
Regulon
Archaea transcription regulation…
Similar to bacteria
sensing local density of cells through secretion/detection of specific molecules
Quorum sensing
