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55 Cards in this Set
- Front
- Back
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How many sigma factors does e. Coli have |
7 |
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How many sigma factors does streptomyces have |
About 60 |
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What do alternative sigma factors allow for |
Allows coordination expression of a set of genes involved in a common process |
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How can changes in life style affect sigma use |
Bacillus sporulation E. Coli stationary phase Motility, stress responses, pathogenicity |
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What does the inappropriate production of small amounts of alternative signals factors |
They are more tightly regulated by- Transcriptional control Translational control Synthesis of inactive pro sigma requiring proteolytic activation The presence of anti sigma factors Phosphorylation |
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What does the activation of master transcriptional regulator Spo0A lead to |
To the sequential activation of sigma F in the forespore, sigma E in the mother cell, sigma G in the forespore , and sigma K in the mother cell |
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What does sigma E control |
Expression of genes required for cell envelope homeostasis |
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What is sigma E important for |
Pathogenesis ie. Defence against anti microbial peptides, ROS |
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What is an inducer |
Substance that induces enzyme synthesis |
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What is a corepressor |
Substance that repressed enzyme synthesis |
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What do activator proteins bind to and do |
Bind to Activator binding sites and alter DNA structure to facilitate better contact or recognition. They can also bind to RNAP directly |
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What is DNA looping important for |
Important for activation of transcription from sigma 54- dependent promoters; ara regulation |
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What makes activator proteins bind to DNA better |
When the inducer is present it allows DNA to bind better |
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What does the inducer do for DNA to allow it to bind |
Ensures that gene expression occurs in response to the correct stimuli When the Intracellular concentration of inducer falls below a certain level, the activator dissociates and can no liver contact RNAP to stimulate transcription of the target gene |
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What is MalT |
Inducer |
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What is the mechanics of repressors |
Bind operators and repress transcription from the promoter Either by preventing RNAP from accessing the promoter or by modulation activity of an activator protein |
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What does relief from repression require |
The presence of an inducer |
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What is induction |
Increases expression of the target gene |
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What makes repressor bind properly |
Repressor binds poorly unless first bound by corepressor |
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What is derepression |
Gene expression triggered by release of the corepressor and respressor |
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What does ArgR control |
Expression of 19 transcription units in E. Coli |
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What is an allosteric repressor protein |
Confirmation changes upon binding of the co repressor arginine |
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What is active form |
Hexameter bound to arginine ArgR+ arginine binds palindromic operator sequences called ARG boxes |
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What does lacl do |
Encodes the repressor protein Lacl |
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What is the lac operon |
lacZ lacY lacA |
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What does lacZ do |
Encodes beta galactosidase |
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What does lacY do |
Encodes lactose permease |
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What does lacA do |
Unclear |
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What is lacL repressor |
Helix turn helix DNA binding protein |
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How is lacL expressed and how is it’s activity |
Expressed constitutively Activity is modulated |
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What happens in the absence of lactose in lac operon |
LacL tetramer binds two operator sites and represses lacZYA transcription |
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What is the inducer of lac operon |
Allolactose |
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What is allolacotse similar to |
Structurally similar to IPTG can act as a gratuitous inducer |
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What does alloactose do to the repression of the lac operon |
Alleviates repression of the lac operon It binds lacL and alters it’s conformation so that it no longer binds |
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When is lactose not utilised in E. Coli |
Lactose is not used when the preferred carbon source glucose is present |
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What happens when a preferred carbon source is present |
Carbon catabolic gene clusters are repressed |
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What is catabolite repression |
Also known as the glucose effect |
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What is catabolite repression an indirect result of |
Indirect result if a better carbon source being present |
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What is cAMP |
Second messenger which is synthesised from ATP by adenylate Cyclades |
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What happens if glucose is present and inhibits adenylate Cyclase |
No cAMP synthesis |
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What happens if glucose is absent in the adenylate cyclase is active |
It can make cAMP |
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What is the other name for CRP |
CAP |
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What is CRP |
cAMP receptor protein |
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What does CAP stand for |
Catabolite activator protein |
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What type of activator Protein is CRP |
Positive |
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What can CRP only bind to if DNA is bound to it |
Can only bind to DNA if cAMP is bound to it |
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What can RNAP only be bind to catabolite repressed promoters if what is bound first |
CRP needs to be bound first |
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What requires inducer exclusion |
In addition to cAMP-CRP regulation of gene expression, catabolite repression |
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What happens when glucose is transported into the cell in catabolite repression |
When glucose is transported into the cell, EllA inhibits uptake of lactose by LacY (no inducer for lac gene expression present in cell) |
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What are the four genes ara locus consists of |
araCBAD |
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What is araC transcribed from |
It’s own divergent promoter |
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When does araC adopt different confirmations |
When bound by the effector Arabinkse |
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What happens to AraC in the absence of arabinose |
AraC exerts negative control |
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What happens to AraC in the presence of arabinose |
It exerts positive control |
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What does AraC undergo in the presence of arabinose |
Conformational change Binds go aral1 and aral2 Repression loop is disrupted Operon is derepressed |
