Week 3: Regulation of bacterial gene expression by small molecule signalling - cAMP

Question 1

What is CRP?

Answer 1

cAMP receptor protein

allows cAMP to bind genes via binding to the CRO

Question 2

What does cAMP biding to CRP cause?

Answer 2

allosteric activation

Question 3

Where does cAMP-CRP bind to on genes?

Answer 3

cAMP-CRP binds to a conserved ‘CRP binding site’ in the promoter of cAMP-responsive genes, activating (usually) their transcription

Question 4

What is an example of cAMP-CRP binding genes and causing activation of genes?

Answer 4

cAMP-CRP activates expression of the lacZYA operon to promote utilisation of lactose

Question 5

What 2 things need to happen to activate the Lac operon?

Answer 5

1. lactose present in cell. allolactose (metabolite of lactose), binds to the LacI repressor protein, causes it to fall of the lacI promoter.
2. cAMP levels have increased in the cell (if no glucose present) binds to CRP and camp-CRP complex can bind the Lac operon promoter
3. This allows the RNA polymerase to.

Allows the polycistronic Lac message to be transcribed

Question 6

What is allolactose?

Answer 6

metabolite of lactose
inducer of lactose

Question 7

Can cAmp- CRP promote transcription?

Answer 7

YES
CAMP-CRP bind to their specific CRP-binding site on the DNA. this helps t bend the DNA round and the camp-CRP binds to the alpha-subunit of RNA-polymerase.

and activation of RNA polymerase.

transcription promoted

Question 8

What 2 pathways can cAMP regulate?

Answer 8

1. housekeeping function of metabolite repression
2. virulence gene expression

Question 9

What are typical calcium conditions inside a host?

Answer 9

low

Question 10

What do low Ca2+ conditions inside a host activate?

Answer 10

2 adenylate cyclases

CyaA and CyaB

Question 11

What does the activation of CyaA and CyaB promote?

Answer 11

activation of adenylate cyclase production.

increase in camp production

Question 12

What does cAMP bind to in the virulence gene expression pathway?

Answer 12

Vfr (pseudomonas CRP)

Question 13

What does the camp-Vfr complex have an effect on?

Answer 13

variety of downstream genes.

1. increased expression of a Type 3 secretion system
2. increased expression of type IV pili
3. increased expression of other virulence genes.
4. repression of motility
5. transcription of CbdA

Question 14

What enzyme is involved in a feedback loop in virulence gene expression?

Answer 14

CpdA

inhibits camp

stops camp getting to high.

makes sure you have the signals to maintain the high camp levels

Question 15

What is CpdA?

Answer 15

phosphodiesterase

Question 16

What message is transcribes by the Lac operon?

Answer 16

polycistronic message

Question 17

When is lactose operon promoted?

Answer 17

when no glucose present in cell. The adenosine cyclase is activated and the lac operon promoted by cAMP.

Question 18

What 2 activities in a cell cam cAMP regulate?

Answer 18

housekeeping function (catabolite repression) and virulence

Question 19

What is a T3SS?

Answer 19

The type III secretion system (T3SS or TTSS), also called the injectisome, is one of the bacterial secretion systems used by bacteria to secrete their effector proteins into the host’s cells to promote virulence and colonisation. The T3SS is a needle-like protein complex found in several species of pathogenic gram-negative bacteria.

Question 20

How is camp involved in catabolite repression?

Answer 20

The activated cAMP–Crp complex induces the promoters of enzymes that catabolise less preferred carbon sources… lactose