TOXINS

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TOXINS
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Exotoxin

• Secreted form the pathogen

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Endotoxin

• Bound to the pathogen surface

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Functional types of toxin

• Cytotoxin
• Neurotoxin
• Leukotoxin
• Cardiotioxin
• Define the target cell

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Name related to source

• Shiga toxin Shigella sp.
• Cholera toxin Vibrio cholerae
• Tetanus toxin Clostridium tetani

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Name related to function

• Type I
• Binds to host cell and elicits an effect e.g.
  superantigen.
• Type II
• Destroys membranes e.g. pore formers
  phospholipases
• Type III
• A-B type
• B region binds to cell A region translocates and
  causes effect

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Type I
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Type II

• Pore formers

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Type III

• A-B toxins

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Structure of the botulinum toxins
Structure of the botulinum toxins
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The A component of most A-B toxins catalyzes
ADP-ribosylation of host cell target proteins.
The ADP-ribosyl group is removed from the
coenzyme NAD (see dashed line) and is covalently
attached to a host cell target protein. This
causes the inactivation of that target protein.
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Key concepts.

• Toxins can be secreted or cell bound.
• Three major types that have distinct modes of
  action.
• Toxin targets cells that have a receptor for
  toxin.
• A-B toxins have distinct binding and functional
  domains