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E. coli Stress Response Flashcards

1
Q

Roles of EC fell envelope?

A

Signal Transduction ~

Energy, Metabolism, Respiration

Defence, Protection, Resistance

Elongation, Shape, Motility

Virulence, Attachment, Biofilm

Transport, Selection, Chemotaxis,
Separation

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2
Q

Outline the basic EC envelope structure (draw)

A

(OM:)
Lipopolysaccharide - LPS
Phospholipid - PL

(PP:)
Peptidoglycan Cell Wall - PG

(IM:)
Phospholipid - PL
Phospholipid - PL

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3
Q

Where are active transporters found? What do they do?

A

They transport OUT AND IN

They are across OM, IM and spanning between them

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4
Q

What are porins? Where are they found?

A

They are passive transporters
(hphilic molecules - permeable)

They are in OM

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5
Q

Where are Lipoproteins? What do they do?

A

They are anchored between PG and PL layers

They do lots of stuff
Sig Trans, nutrients, transport, etc

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6
Q

Where are proteases? What do they do?

A

Eat inactive proteins

They are in PP and IM

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7
Q

Where are chaperones? What do they do?

A

They fix wrongly-folded proteins

They are in PP

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8
Q

Where is the highest density of proteins in E. coli?

A

The periplasm (PP)

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9
Q

What kinds of stress can trigger response in bacteria?

A
  1. Environmental
  2. Membrane permeability
  3. Problems with proteins
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10
Q

What does the sigma E response help with?

A

OM defects

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11
Q

What does the CpxAR response help with?

A

IM + PP defects

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12
Q

What does the Phage Shock Protein (Psp) response help with?

A

IM permeability

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13
Q

What does the BaeSR response help with?

A

Pump out damaging agents

efflux pumps

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14
Q
  • What does the PhoPQ response help with? (Non-Env system)
A

LPS defects

Activated My MicA!

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15
Q

What does the Outer Membrane Vesicle response help with?

Why is it different from ever response systems?

A

Increases hydrophobicity

Different because it does not involve activation of genes

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16
Q
  • What IS sigma E?
A

An alternate Sigma Factor which controls extracytoplasmic stress response.

It enables RNA pol to increase TS of certain genes

Previously thought to only be essential at high temperatures, but it’s ESSENTIAL at all

17
Q
  • What is the role of the Sigma E system?
A

Maintain HOMEOSTASIS of outer membrane

By monitoring OM protein BIOGENESIS

18
Q

What are the actors in the Sigma E system?

A

RseA - antisigma

RseB - negative reg

DegS - protease (PP domain)

RseP - protease (IM domain)

Clp XP - protease (Cytoplasm)

19
Q

What physical stresses will active the Sigma E system?

A

Heat
Ethanol
Growth phase

20
Q

What do the stresses to do the OM Which activates the Sigma E system?

A

Misfold OMPs and LPS

Proteins end up in cytoplasm

YxF domain of PORIN is exposed

21
Q

What do the Perplasmic LPS and Porin YxF do to activate the Sigma E system?

A

LPS takes away RseB -
RseA is vulnerable

YxF activates DegS -
DegS noms RseA

~ PP domain only (1/3) ~

22
Q

How are the domains of RseA destroyed?

A

Once PP region is vulnerable, activate DegA noms it (1/3)

RseP noms IM domain (2/3)

CP domain now free in CP, nommed by ClpXP, releasing Sigma E (3/3)

23
Q

What is the PRO-TS of Sigma E?

A

Activate >100 Genes to REGULATE OMP Synthesis

Increase Chaperones and Proteases
(get rid of stress)

Increase OMP biogenesis
(New, Good proteins)

Increase TPort machinery
(Get rid of broken proteins)

Other TS regulators
(communication)

24
Q

How does Sigma E get Positive and Negative feedback?

A

Activates its OWN regulon:

rpoE (encodes Sigma E)

rseABC (captuses Sigma E)

25
Q

What is the ANTI-TS action of Sigma E?

A

Use sRNAs

Decrease synth and accumulation
of OMP and LPPs

26
Q

Describe the sRNAs

A

50-300nt (in bac)

Fast!

Need RNA chaperone - Hfq

27
Q

What is Hfq?

A

An RNA chaperone that helps sRNAs

28
Q

What 3 ways can an sRNA//Hfq REPRESS expression?

A
  1. Prevent TL
    (mRNA ribosome site)
  2. Promote mRNA Degradation
    (sRNA is a signal)
  3. Act on (+) regulator
29
Q

What 3 ways can an sRNA ACTIVATE expression?

A
  1. Free mRNA Ribosome site

(hidden by 2* Structire - sRNA anneals to it)

  1. Impede degradation of sRNA (binds to unstable RNA to prevent RNAse)
  2. Sequester a (-) regulator
30
Q

What are the three key sRNAs?

A

RybB (1-component)

MicA (2-component)

MicL (2-component)

31
Q

What does RybB do when Sigma E activates its production?

A

Repress OM protein synthesis

32
Q

What does MicA do when Sigma E activates it?

A
  1. Repress OM protein production
  2. Repress PhoPQ (2-comp) -

Prevent repair of LPPs

33
Q

What does MicL do when Sigma E activates its production?

A
  1. Repress OM Lpp

2. (-) feedback for Sigma E!

Molecular Genetics (5 decks)

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