EXOTOXIN1 - immune responses. Staphylococcal toxins act...

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EXOTOXINS Exotoxins are also classified based on structure and function:    1. A-B toxins (type III toxins)—largest group, these have 2 parts, A and B. A is the active  enzyme component and B is the binding component. B binds to a receptor on the host cell and  both parts are transported into the cell. The two parts separate and A does the damage.      2. Membrane-disrupting toxins (type II toxins)—disrupt the plasma membrane and cause lysis  of the cell, either by forming channels through the plasma membrane or disrupting the  phospholipids of the membrane.          a. Leukocidins are membrane-disrupting toxins that kill phagocytic white blood cells  (leukocytes)         b. Hemolysins are toxins tht kill red blood cells.      3. Superantigens (type I toxins)—antigens tht provoke a very intense immune response. T cells  are stimulated to release enormous amounts of cytokines, which cause harm instead of enhiacing 
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Unformatted text preview: immune responses. Staphylococcal toxins act this way. Some major exotoxins: 1. Diphtheria toxin---Corynebacterium diphtheriae produces this toxin when it is carrying a lysogenic phage which includes the tox gene. This is a cytotoxin which inhibits protein synthesis as follows: a. The toxin consists of 2 different polypeptides combined, A (active) and B (binding). A is the one which actually causes the harm to the host, but it cannot act without B also being present. b. Polypeptide B binds to surface receptors on the host cell and causes the transport of both parts across the plasma membrane into the cell. c. The two parts separate d. Polypeptide A inhibits protein synthesis inside the cell....
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EXOTOXIN1 - immune responses. Staphylococcal toxins act...

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