L6. Toxins

Question 1

what are AB toxins?

Answer 1

B joins to host cell receptor - binding subunit - tropism for specific cell receptors - translocated A inside the cell

A is internalised into the cell - enzymatic/active subunit - forms protein-protein interactions inside the cell

Question 2

what are the two favoured structures of AB toxins and why?

Answer 2

A1B1​

simple A-B toxin (usually portions are synthesised as single pretoxin polypeptide)​

A1B5 ​

compound A-B toxin​
(separate genes for each subunit) ​

Question 3

What are pore-forming toxins?

Answer 3

largest
can also act as superantigens
disrupt membrane to form pores
lose osmotic balance via a loss of ions
form a spore in non-optimal conditions to resist cell death - resistant to antibiotics/temp

Question 4

superantigens

Question 5

endotoxins (LPS)

Answer 5

on cell surface

Question 6

exotoxins

Answer 6

produced inside the cell and secreted

Question 7

What is the name of the toxin produced by Clostridium botulinum, and what type of toxin is it?

Answer 7

Botulinum toxin; AB toxin / Neurotoxin

Question 8

Describe the mechanism of action of botulinum toxin.

Answer 8

The heavy chain binds to presynaptic receptors on neurons, facilitating the passage of the light chain into the cell. The light chain disrupts the release of acetylcholine, resulting in neuromuscular blockade.

Question 9

How does botulism differ from tetanus in terms of the type of paralysis caused?

Answer 9

Botulism causes flaccid paralysis, while tetanus causes spastic paralysis.

Question 10

compare rigid an flaccid paralysis

Question 11

What is the general effect of pore-forming toxins on host cells?

Answer 11

Pore-forming toxins disrupt the membrane of host cells, leading to membrane permeability, ion imbalance, and ultimately cell lysis.

Question 12

Name two categories into which pore-forming toxins are generally divided based on their structural architecture.

Answer 12

Alpha-pore-forming toxins and Beta-pore-forming toxins.

Question 13

Give an example of a bacteria and the corresponding pore-forming toxin it produces.

Answer 13

Bordetella pertussis produces adenylate cyclase toxin (RTX class).

Question 14

What are superantigens, and how do they induce an extreme immune response?

Answer 14

Superantigens are secreted protein toxins that bind to MHC class II and T cell receptors, activating many T cells simultaneously. This leads to the release of excessive proinflammatory cytokines into the bloodstream.

Question 15

what are the 3 different types of exotoxins?

Answer 15

A-B toxins​

Membrane-disrupting toxins (pore-forming)​

Superantigens​

Question 16

what are some bacteria that have superantigens?

Answer 16

gram pos - induce shock to dysregulate immune system