STRUCTURE AND MODE OF ACTION OF CYTOLYTIC,NEURO,ENTERO & ENDOTOXINS

1. JBAS COLLEGE FOR WOMEN CHENNAI
Dr Sumitha J
TOXINS

2. Bacterial toxins: Bacterial toxins are produced by bacteria and can be classified into
two main types:
Endotoxins: These toxins are found in the cell wall of Gram-negative bacteria and are
released when the bacteria are killed or damaged. They are made up of a complex
molecule called lipopolysaccharide (LPS). LPS is a very large molecule that is made up
of a lipid and a polysaccharide. The lipid portion of LPS is responsible for the toxicity
of the endotoxin.
Exotoxins: These toxins are released by living bacteria. They can be released during
the growth of the bacteria or when the bacteria are killed or damaged. Exotoxin are a
more diverse group of toxins than endotoxins. They can be made up of proteins,
peptides, or nucleic acids.
TOXINS

3. Bacterial toxins can be classified based on their mode of action into five main categories:
Cytotoxins: These toxins damage cells. They can do this by disrupting cell membranes,
interfering with protein synthesis, or causing cell death.
Enterotoxins: These toxins damage the lining of the intestines. They can do this by increasing the
production of water and electrolytes in the intestines, which leads to diarrhea.
Hemolysins: These toxins destroy red blood cells. They can do this by punching holes in the cell
membrane, which allows the contents of the cell to leak out.
Neurotoxins: These toxins damage the nervous system. They can do this by blocking nerve
signals or interfering with neurotransmitters.
Superantigens: These toxins activate the immune system in a way that is harmful to the body.
They can do this by binding to certain white blood cells and causing them to release large
amounts of cytokines, which are proteins that promote inflammation.
TOXINS

4. Bacterial toxins can be single proteins or organized as oligomeric protein complexes
and are organized with distinct AB structure-function properties.
The A domain encodes a catalytic activity; ADP-ribosylation of host proteins is the
earliest post-translational modification determine to be performed by bacterial toxin,
and now include glucosylation and proteolysis among other s. Bacterial toxins also
catalyze the non-covalent modification of host protein function or can modify host cell
properties through direct protein-protein interactions.
The B domain includes two functional domains: a receptor-binding domain, which
defines the tropism of a toxin for a cell and a translocation domain that delivers A
domain across a lipid bilayer, either on the plasma membrane or the endosome.
Bacterial toxins are often characterized based upon the section mechanism that
delivers the toxin out of the bacterium, termed type I–VII
TOXINS

5. TYPES I TO VII TOXIN

6. Heat-labile toxins: These toxins are typically proteins that are denatured by heat. This
means that they lose their structure and function when they are exposed to heat. Heat-
labile toxins are often used by bacteria to cause diseases such as food poisoning and
cholera.
Heat-stable toxins: These toxins are typically proteins that are resistant to heat
denaturation. This means that they do not lose their structure and function when they
are exposed to heat. Heat-stable toxins are often used by bacteria to cause diseases
such as tetanus and botulism.
HEAT STABILITY

7. These toxins damage or kill cells. They can do this by disrupting cell membranes,
interfering with protein synthesis, or causing cell death. Some examples of cytolytic
toxins include:
Botulinum toxin: This toxin is produced by the bacterium Clostridium botulinum and is
the most potent toxin known. It can cause paralysis by blocking the release of
acetylcholine, a neurotransmitter that is essential for muscle contraction.
Tetanus toxin: This toxin is produced by the bacterium Clostridium tetani and causes
muscle spasms. It does this by blocking the release of glycine, an inhibitory
neurotransmitter.
Streptococcal pyrogenic exotoxins (Spe): These toxins are produced by certain strains
of Streptococcus pyogenes and can cause fever, shock, and organ failure. They do this
by activating the immune system and causing the release of inflammatory mediators.
CYTOLYTIC TOXINS

8. The mode of action of cytotoxins can also vary depending on the type of toxin.
However, some common mechanisms include:
Disrupting cell membranes: Cytotoxins can disrupt cell membranes by forming pores
or by causing the cells to swell. This can lead to cell death.
Interfering with protein synthesis: Cytotoxins can interfere with protein synthesis by
blocking the synthesis of essential proteins or by destroying ribosomes. This can lead
to cell death.
Causing cell death: Cytotoxins can cause cell death by activating the cell's death
program, called apoptosis.
CYTOLYTIC TOXINS

9. Botulinum toxin: This toxin is produced by the bacterium Clostridium botulinum and is the most
potent toxin known. It can cause paralysis by blocking the release of acetylcholine, a
neurotransmitter that is essential for muscle contraction.
Tetanus toxin: This toxin is produced by the bacterium Clostridium tetani and causes muscle
spasms. It does this by blocking the release of glycine, an inhibitory neurotransmitter.
Streptococcal pyrogenic exotoxins (Spe): These toxins are produced by certain strains of
Streptococcus pyogenes and can cause fever, shock, and organ failure. They do this by activating
the immune system and causing the release of inflammatory mediators.
Shiga toxin: This toxin is produced by the bacterium Shigella dysenteriae and causes dysentery. It
does this by damaging the lining of the intestines.
Pseudomonas aeruginosa exotoxin A: This toxin is produced by the bacterium Pseudomonas
aeruginosa and can cause a variety of infections, including pneumonia and sepsis. It does this by
damaging cells in the lungs and other organs.
CYTOLYTIC TOXINS

10. Structure: Enterotoxins are a type of exotoxin that is produced by bacteria. They are
proteins that can cause damage to the lining of the intestines.
Enterotoxins are typically small proteins, with a molecular weight of less than 100,000
daltons. They are often made up of multiple subunits, which can be either soluble or
membrane-bound.
ENTEROTOXINS

11. Mode of action: Enterotoxins can damage the lining of the intestines in a variety of ways. Some
enterotoxins can cause cells to swell and burst, while others can disrupt cell membranes.
Enterotoxins can also interfere with protein synthesis or activate the immune system.The specific
mode of action of an enterotoxin depends on the type of toxin. However, some common
mechanisms include:
Swelling and bursting of cells: Some enterotoxins can cause cells to swell and burst. This can
lead to the release of toxins and enzymes that can damage the lining of the intestines.
Disrupting cell membranes: Some enterotoxins can disrupt cell membranes. This can lead to the
leakage of essential molecules out of cells, which can cause cell death.
Interfering with protein synthesis: Some enterotoxins can interfere with protein synthesis. This
can lead to the death of cells that require protein synthesis to survive.
Activating the immune system: Some enterotoxins can activate the immune system. This can lead
to inflammation and damage to the lining of the intestines.
ENTERO TOXINS

12. Vibrio cholerae toxin: This toxin is produced by the bacterium Vibrio cholerae and
causes cholera. It does this by increasing the production of water and electrolytes in
the intestines, which leads to diarrhea.
E. coli heat-stable enterotoxin (ETEC): This toxin is produced by some strains of
Escherichia coli and causes traveler's diarrhea. It does this by increasing the
production of water and electrolytes in the intestines, which leads to diarrhea.
Staphyloccocal enterotoxin B (SEB): This toxin is produced by the bacterium
Staphylococcus aureus and can cause food poisoning. It does this by increasing the
production of water and electrolytes in the intestines, which leads to diarrhea
ENTERO TOXINS

13. These toxins cause damage to the lining of the intestines. They can do this by
disrupting cell membranes, interfering with protein synthesis, or causing cell death.
Some examples of enterotoxins include:
Vibrio cholerae toxin: This toxin is produced by the bacterium Vibrio cholerae and
causes cholera. It does this by increasing the production of water and electrolytes in
the intestines, which leads to diarrhea.
E. coli heat-stable enterotoxin (ETEC): This toxin is produced by some strains of
Escherichia coli and causes traveler's diarrhea. It does this by increasing the
production of water and electrolytes in the intestines, which leads to diarrhea.
Staphyloccocal enterotoxin B (SEB): This toxin is produced by the bacterium
Staphylococcus aureus and can cause food poisoning. It does this by increasing the
production of water and electrolytes in the intestines, which leads to diarrhea.
ENTEROTOXINS

14. These toxins damage the nervous system. They can do this by blocking nerve signals,
interfering with neurotransmitters, or causing cell death. Some examples of neurotoxins
include:
Ricin toxin: This toxin is produced by the castor bean plant and is one of the most toxic
substances known. It can cause respiratory failure and death by blocking protein
synthesis in cells of the nervous system.
Scorpion venom: Scorpion venom contains a variety of toxins that can cause a range of
symptoms, including paralysis, pain, and death. Some of these toxins can damage the
nervous system by blocking nerve signals or interfering with neurotransmitters.
Snake venom: Snake venom contains a variety of toxins that can cause a range of
symptoms, including paralysis, bleeding, and death. Some of these toxins can damage
the nervous system by blocking nerve signals or interfering with neurotransmitters.
NEUROTOXINS

15. Neurotoxins can damage the nervous system in a variety of ways. Some neurotoxins can block
nerve signals, while others can interfere with neurotransmitters. Neurotoxins can also cause cell
death.
The specific mode of action of a neurotoxin depends on the type of toxin. However, some common
mechanisms include:
Blocking nerve signals: Some neurotoxins can block nerve signals by binding to specific
receptors on nerve cells. This can prevent the release of neurotransmitters, which are chemicals
that allow nerve cells to communicate with each other.
Interfering with neurotransmitters: Some neurotoxins can interfere with neurotransmitters by
destroying them or by blocking their receptors. This can also prevent nerve cells from
communicating with each other.
Causing cell death: Some neurotoxins can cause cell death by activating the cell's death program,
called apoptosis
NEUROTOXINS

16. Botulinum toxin: This toxin is produced by the bacterium Clostridium botulinum and is
the most potent toxin known. It can cause paralysis by blocking the release of
acetylcholine, a neurotransmitter that is essential for muscle contraction.
Tetanus toxin: This toxin is produced by the bacterium Clostridium tetani and causes
muscle spasms. It does this by blocking the release of glycine, an inhibitory
neurotransmitter.
NEUROTOXINS

17. These toxins damage the blood. They can do this by disrupting blood clotting,
destroying red blood cells, or causing other problems. Some examples of hemotoxins
include:
Staphylococcal alpha-toxin: This toxin is produced by the bacterium Staphylococcus
aureus and can cause toxic shock syndrome. It does this by disrupting blood clotting
and causing inflammation.
E. coli verotoxin (VT): This toxin is produced by some strains of Escherichia coli and
can cause hemolytic uremic syndrome. It does this by destroying red blood cells and
causing kidney damage.
Vibrio vulnificus toxin: This toxin is produced by the bacterium Vibrio vulnificus and
can cause necrotizing fasciitis. It does this by destroying tissue and causing
inflammation.
HEMATOXINS