Virulence Regulation I Flashcards Preview

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Flashcards in Virulence Regulation I Deck (31):
1

What is an example of how bacterial genes adapt to the host environment?

Siderophores allowing them to scavenge the host for Fe

2

Virulence Factor

Any bacterial property required for entry, growth, or survival in a HOST - not necessarily required for life in the lab

3

What are examples of virulence factors?

• capsule - inhibits killing by complement
• adhesins - permit adherence to host cells
• acid tolerance factors (ASPs) - adapt pathogen to stomach
• enzymes - synthesize unavailable nutrients

4

Virulence Gene

Genes that encode virulence factors

5

Pathogenicity Islands

Large, localized regions of chromosome missing in related non-pathogens

6

Operator

Binding site for a transcription factor

7

Operon

Operon is a unit of transcription that includes more than one cistron

8

Multicistronic mRNA

It is the mRNA that results from transcription of a multicistronic operon

9

RNA polymerase

Transcribes DNA into mRNA.

10

σ (sigma) Factor

It is subunit of RNAP that specifically recognizes and binds the promoter

11

What binds to the promoter?

The RNAP holoenzyme (entire unit binds via sigma factor)

12

Closed Complex

The product of the RNAP/DNA interaction

13

Open Complex

Once bound, RNAP causes the double strand of DNA to open

14

What part of transcription is primarily regulated?

Initiation

15

What happens to cAMP as glucose decreases?

cAMP increases

16

What happens to cAMP as glucose increases?

cAMP decreases

17

What happens in the lac operon with glucose present and cAMP absent?

Repression of the operon by steric hindrance as lacR is transcribed and made into the repressor protein.

18

How does induction occur in the lac operon?

The inducer, in this case, lactose, will bind to the represser to prevent it from binding DNA.

Then, conditions need to be right with glucose absent and cAMP present, which will lead cAMP to bind CRP into cAMP-CRP which is the activator and recruits RNAP.

19

What is required for induction of the lac operon?

1) Lactose presence
2) Glucose absence -> high cAMP

20

What does RNAP bind?

Promoter

21

What does the repressor bind?

Operator - repressor binding will reduce the affinity of RNAP binding

22

What does the inducer bind?

Repressor - inducer binding will decrease the repressor's binding affinity

23

What does the activator bind?

Activator interacts with RNAP and increases RNAP affinity

24

What does the co-factor bind?

In the lac operon, cAMP is the co-activator.

Co-activator binds the activator and increases the activator's binding affinity

25

What happens to the probability of transcription as the stability of the closed complex increases?

The probability of transcription initiation increases as the stability of the closed complex increases.

activators increase stability
repressors decrease stability

26

Holoenzyme

σ + core enzyme (RNAP)

27

Core Enzyme

2 α subunits, 1 β subunit, β’ subunit

28

Regulon

A group of operons (also called a global control system) subject to the control of a common (or global) regulator

29

What is the purpose of a regulon?

It allows simultaneous activation and inactivation of a series of related genes

30

Can a repressor protein at Operator A be an activator at Operator B?

Yes

31

Repressors inhibit transcription by
A. increasing the affinity of RNAP for the promoter
B. interfering with the binding of RNAP to the promoter
C. causing RNAP to fall off the promoter
D. none of the above
E. all of the above

B. interfering with the binding of RNAP to the promoter

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