Mci 4: Bacterial Toxins And Secretions

Front 1

What types of small molecule might be secreted by a bacteria?

Back 1

Antibiotics
Siderophores - iron-chelating agents.
Pheromones (signalling molecules)

Front 2

Through what type of molecule is a substance secreted?

Back 2

Drug-efflux proteins
ABC proteins or proton antiporters

Front 3

What is the drug efflux protein in E. Coli? What are the components?

Back 3

AcrAB (AcrA, AcrB and TolC)

Front 4

What types of proteins might be secreted by a bacteria?

Back 4

Hydrolytic enzymes (degrade extracellular polymers)
Components of flagella and pili
Exotoxins involved in pathogenesis
Bacteriocins (kill related bacteria)

Front 5

What is Type 1 protein secretion?

Back 5

Each target protein has its own ABC transporter.

Front 6

How is export across the plasma and outer membranes done in one step in Type 1 protein secretion?

Back 6

Using membrane fusion protein
Using outer membrane protein

Front 7

What is an example of Type 1 protein secretion? What type of molecule are they? Is ATP used?

Back 7

E. Coli haemolysin HlyA and colicins.
Bacteriocins.
ATP is used.

Front 8

What are the components of the HlyA movement system?

Back 8

TolC, HlyB and HlyD.

Front 9

What is the general secretory pathway?

Back 9

A pathway shared by many target proteins.

Front 10

How are targets for the general secretory pathway identified?

Back 10

By the N-Terminal Signal sequence.

Front 11

How is the GSP chaperoned?

Back 11

By SecB or a Signal Recognition Particle (from translation)

Front 12

What is the translated protein being fed through? What region is it entering? Does it require energy?

Back 12

The SecYEG pore. Entering the periplasm. Energy is required.

Front 13

Where does the energy come from?

Back 13

SecA ATPas and maybe proton channel SecDF.

Front 14

What component removes the 'leader protein'?

Back 14

Lep

Front 15

When can the protein fold in the periplasm?

Back 15

Once the leader protein has been removed.

Front 16

What alternative system exports the proteins with cofactors?

Back 16

The Twin-Arginine Transport system (TAT system).

Front 17

How are proteins sent to Type 2, or Main Terminal Branch Secretion?

Back 17

Proteins destined for secretion by the periplasm are recognised by unknown criteria and sent.

Front 18

How is the pore formed in the periplasm in Main Terminal Branch Secretion?

Back 18

From subunits of protein D.

Front 19

Once the secretory molecule has entered the pore, what happens?

Back 19

A pilin-like subunit assembles to form a piston to push the protein out.

Front 20

What is Type 2 secretion used for?

Back 20

Some extracellular hydrolytic enzymes and some toxins.

Front 21

What structure does the Type 3 secretion machinery resemble?

Back 21

That used to synthesise the flagella.

Front 22

What type of molecule does the Type 3 secretion system secrete?

Back 22

Toxins (used by pathogens to inject toxins into host cells).

Front 23

What is an example of a Type 3 secretion system?

Back 23

Enteropathogenic E. Coli this secretion to inject a receptor (Translocated Intimin Receptor, TIR) into host cell, and then use their own intimin to bind to it.

Front 24

What are two other names for type 3 secretion?

Back 24

TTSS
Injectisome

Front 25

What is the Type IV secretion system related to?

Back 25

Machinery used to export DNA:protein complexes during conjugation.

Front 26

How is it used by pathogens?

Back 26

Used to inject toxins into host cells.

Front 27

What is an example of the Type IV secretion system?

Back 27

Agrobacterium tumefaciens to transport T-DNA and associated proteins into plant cells.

Front 28

What are the two types of bacterial toxin?

Back 28

Endotoxin
Exotoxin

Front 29

What is an endotoxin? How is it recognised?

Back 29

The lipopolysaccharide of the outer membrane. Recognised by the innate immune system.

Front 30

What are exotoxins?

Back 30

Secreted toxins.

Front 31

What are the 5 types of exotoxin?

Back 31

Cytolytic toxin
Cytotoxin
Neurotoxin
Enterotoxin
Superantigens

Front 32

What do cytolytic toxins do?

Back 32

Damage host cell membrane integrity.
OR Form pores.

Front 33

What do cytotoxins do?

Back 33

Kill cells.

Front 34

What is an example of a cytolytic toxin that forms pores? What is its action?

Back 34

Streptolysin O from Streptococcus. Interacts with cholesterol.

Front 35

What is are 2 examples of a cytolytic toxin that damage host cell integrity? What is its action?

Back 35

Phospholipase C from Pseudomonas
Lecithinase from Clostridium

Front 36

What is a Haemolysin?

Back 36

Lyses red blood cells.

Front 37

What is a leukocidin?

Back 37

Lyses white blood cells.

Front 38

What is an AB Toxin?

Back 38

A 2 part toxin consisting of a mixture of A subunits and B subunits.

Front 39

What do the A and B subunits do?

Back 39

A: Active
B: Binding

Front 40

What is the action of an AB toxin?

Back 40

B binds to receptor on cell, causing internalisation of A.

Front 41

What kind of activity do the A subunits usually have?

Back 41

Enzymatic activity.

Front 42

What three toxins may an AB toxin be?

Back 42

Cytototoxins
Enterotoxins
Neurotoxins

Front 43

What is the definition of a neurotoxin?

Back 43

A toxin that kills the host without directly killing cells.

Front 44

How does the Botulinum Toxin work?

Back 44

A subunit binds motor neurones, preventing acetylcholine release and prevents muscle contractions (causing flaccid paralysis).

Front 45

How does the tetanus toxin work?

Back 45

A subunit binds inhibitory neurones, preventing release of inhibitory neurotransmitters, causing muscle contraction (spastic paralysis).

Front 46

What are some types of cytotoxin?

Back 46

Diphtheria toxin
AB toxins

Front 47

What is an example of a cytotoxic pathway (toxin not needed, just pathway)?

Back 47

A subunit can ADP-ribosylate Elongation Factor 2 to prevent host cell protein synthesis.

(EF2 --> EF2-ribose-ADP, inactive)

Front 48

What is an enterotoxin?

Back 48

A toxin that effects the intestinal cells.

Front 49

What is an example of a AB Toxin that is an enterotoxin?

Back 49

A subunit ADP-ribosylates adenylate cyclase, promoting cAMP synthesis and causing secretion of electrolytes, leading to osmotic fluid loss.

Front 50

What is a superantigen?

Back 50

Molecules which bind T Cell receptors and cause massive inappropriate activation of immune cells.

Front 51

What are two examples of a superantigen?

Back 51

Staphylococcus --> toxic shock toxin
Streptococcus --> Toxic shock-like toxin

Front 52

What are the functions of hydrolytic enzymes?

Back 52

Assist invasion by movement through host.

Front 53

What are 3 other types of virulence factors?

Back 53

Polysaccharide capsules
Attachment factors
Siderophores