Bacterial Replication and Transcription 5.3

Question 1

Positive control of transcription is implemented by?

Answer 1

activator proteins

Question 2

activator proteins bind to? enhance? allosterically modified by? does NOT bind unless?

Answer 2

 bind to activator binding sites
 enhance transcription
 Activator protein activity is allosterically modified by inducers
 Activator protein does not bind unless inducer is present

Question 3

Activator binding site is upstream or downstream from promoter

Answer 3

upstream

Question 4

How does an inducer affect positive control activator proteins?

Answer 4

promotes the binding of the activator protein to the activator binding site, and thus stimulates transcription

Question 5

In the case of maltose utilization, what is the inducer? important for what?

Answer 5

maltose

*This system is pertinent in regulons

Question 6

What is ‘regulon’?

Answer 6

term for genes of a pathway that are spread throughout the bacterial chromosome

Question 7

Explain catabolite repression?

Answer 7

• global regulatory mechanism
• helps cells make the most efficient use of different carbon sources
• cells will use glucose first

Question 8

due to catabolite repression, glucose or lactose is used first in a diauxic growth?

Answer 8

glucose
*As the glucose is depleted, the repression is lifted and production of enzymes for catabolism of the second nutrient is started

Question 9

diauxic growth

Answer 9

bacteria exhibit this when there are two energy sources available

Question 10

The lac operon is controlled by?

Answer 10

1) catabolite repression

2) its own specific regulatory system

Question 11

explain lac operon catabolite repression complex

Answer 11

1) requires cyclic AMP to bind to catabolite activator protein (CAP)/ cyclic AMP receptor protein (CRP)
2) CAP/CRP cyclic AMP complex binds upstream of the promoter for the lac operon and recruits RNA polymerase

Question 12

In order for Lac gene transcription to occur, cyclic AMP must bind to?

Answer 12

CAP

Question 13

In cells growing on glucose the level of ____ is low and _____ is not activated

Answer 13

cyclic AMP is low (due to unphosphorylated Enzyme IIA of phosphotransferase system) and CAP is not activated

Question 14

As glucose is used up cyclic AMP? What happens to CAP?

Answer 14

increases (due to phosphorylated Enzyme IIA of phosphotransferase system) and CAP is activated

Question 15

Prokaryotic signal transduction

1) typically involves?
2) a membrane-integrated?
3) a cytoplasmic?
4) activity of response regulator depends on?

Answer 15

1) involves two-component regulatory systems
2) membrane-integrated sensor kinase protein
3) a cytoplasmic response regulator protein.
4) depends on its state of phosphorylation

Question 16

sensor proteins are often? do what?

Answer 16

often kinases (sensor kinase) or associated witha kinase
*transfers the phsphate to the response regulator protein

Question 17

response regulator protein is typically?

Answer 17

a DNA binding protein that acts as a repressor in the PHOSPHORYLATED form

Question 18

kinases do WHAT? like all the time?

Answer 18

phosphorylate stuff! phosphorylate target cytoplasmic proteins OR itself via autophosphoylation in response to environmental conditions

Question 19

Quorum Sensing definition?

Answer 19

a process by which cells are able to detect the accumulation of a released signal and then change their behavior when the signal concentration exceeds a threshold level

Question 20

Why is Quorum Sensing important for cells?

Answer 20

1) allows cells to survey their environment for cells of their own kind.
2) able to sense population size.

Question 21

How can a cell sense population size in Quorum Sensing?

Answer 21

involves the sharing of specific small molecules. Once a sufficient concentration of the signaling molecule is present, specific gene expression is triggered

Question 22

What is a common quorum sensing inducer?

Answer 22

AHL

Question 23

Quorum Sensing can lead to production of?

Answer 23

virulence factors

Question 24

AHLs cross the bacterial membranes largely through?

Answer 24

diffusion

Question 25

AHLs are detected and bound by?

Answer 25

LuxR-type regulatory proteins

Question 26

When/where does AHLs binding occur?

Answer 26

occurs when the AHL acyl chain enters the hydrophobic acyl-binding pocket
of the LuxR protein

Question 27

The AHL/LuxR complex then binds to?

Answer 27

a DNA promoter regulatory region and activates the transcription of several Quorum Sensing (QS) genes in the lux operon

Question 28

Expression of lux-like genes results in a wide range of activities in different bacteria, such as?

Answer 28

light production, virulence, EPS (exopolysaccharide) secretion, motility, and plasmid transfer

Question 29

Explain Staphylococcus production of ArgD and how it leads to virulence proteins.
(5 steps, very long slide)

Answer 29

1. Basal level transcription of the
argABCD operon in Staphylococcus
leads to production of ArgD, the preautoinducing
peptide (AIP).
2. ArgB trims ArgD into the functional AIP
and exports it out of the cell.
3. As the cell population increases, the
AIP concentration increases and binds
to ArgC, leading to autophosphorylation
of ArgC.
4. ArgC-P then activates the
transcriptional activator ArgA by transfer
of a phosphate group.
5. ArgA-P increases transcription of the
argABCD operon as well as activating
the transcription of an RNA that leads to
the production of virulence proteins