Molecular regulation

Question 1

How many steps of molecular regulation are there and what are they?

Answer 1

A. Phase variation (DNA)

B. Transcriptional regulation (RNA)
Most common way they figure out what gets turned on or off by figuring out what genes get transcribed or not

C. Control of mRNA stability (RNA)

D. Translational control (protein)
Control at the level of protein

E. Post-translational control (protein)
Impacts protein levels and productivity

Question 2

What is phase variation?

Answer 2

• Anything on the surface of the cell could be effected by the antibodies
• Antigenic are things that antibodies bind to – flagella
• The bacteria comes with one type of flagellin and your body makes antibodies but then it switches it and then the antibodies are useless
• Recombinase, promote recombination between different regions of the DNA
• fliB and fliA: they are important in making flagella, and when they are expressed only one RNA is made
• when it is flipped around, there is no more promoter and thus the genes (fliB and fliA) will not be expressed anymore and the repressor is gone
• thus the flagellin goes away but since the fliC is not repressed anymore you make a new flagellin
• it is specific recognition sequence
• no signaling going on

Two forms of flagellin gene (H1 &H2)
- Gene inversion: it can flip the DNA sequence

Question 3

What is transcriptional regulation

Answer 3

• they have activators and repressors, and it is another way to regulate the bacteria’s genes for control of production of gene products and activity

Question 4

What do activators do?

Answer 4

The activator (A) and it has an inducer that binds to it and it will bind to an operator, which is a sequence of gene and it will turn on the gene
The activator only works with the inducer (one example of regulation)

Activator only works with the inducer molecule and when it binds to it then it will stimulate transcription

Question 5

what do repressors do

Answer 5

they turn on induction
- Repressor binds to the operator under normal circumstances unless things change where the inducer binds to the repressor protein, and the repressor turns off the genes

induction
- the inducer binds to the repressor and then the genes are turned on again by induction

or

turn on by derepression
- Gene is usually silent with the repressor
- It is turned on again by derepression
- Co-repressor + repressor bind
- They prevent transcription
- The way you get rid of them, the co-repressor has to go away or not have enough
- Trp operon is a specific example

Question 6

What is lac operon

Answer 6

• lac operon encodes proteins necessary for utilization of lactose
• lactose is the only thing you can eat then you have to make machinery to break down the lactose, but bacteria would prefer glucose
• they will not make the machinery if they do not know that there is lactose and they wont if there is glucose
• There’s no point in making proteins meant to utilize lactose if lactose is not present!
• Glucose is a better energy source

Question 7

what are the modes of regulation for lac

Answer 7

1. Induction: lactose induces expression of the lac operon (lactose is an inducer, binds a repressor)
2. Activation: starvation contributes to expression of the lac operon (cAMP is an inducer, binds an activator)
   * Cyclic AMP
   * Both induction and activation occur at the same time
3. 3. Catabolite repression: glucose inhibits import of lactose into cell (and therefore induction of lac operon)
      * One nutrient will inhibit another nutrient
      * Shuts down the primase that brings lactose into the cell

Question 8

How does lac get induction?

Answer 8

• If lactose is present, lactose is not the inducer, but the product of it
• Allolactose, B-galactosidase changes lactose to allolactose
• How does the enzyme know to change, concentration
• Allolactose binds to the repressor lac I and makes the repressor leave
• And then the RNA polymerase can attach to it, and then transcription can occur
• The RNA that gets made has multiple coding