A-B exotoxin
Definition
A-B exotoxins are a class of bacterial toxins composed of two subunits: the A subunit, which is enzymatically active, and the B subunit, which binds to host cell receptors. These toxins disrupt cellular functions and can cause severe damage to respiratory tissues.
5 Must Know Facts For Your Next Test
- A-B exotoxins are produced by bacteria such as Corynebacterium diphtheriae and Bordetella pertussis, both of which cause serious respiratory infections.
- The A subunit typically interferes with internal cellular processes by modifying host cell proteins or signaling pathways.
- The B subunit determines the specificity of the toxin for particular cell types by binding to specific receptors on the host cell surface.
- Diphtheria toxin (produced by Corynebacterium diphtheriae) is an example of an A-B exotoxin that inhibits protein synthesis in host cells.
- Pertussis toxin (produced by Bordetella pertussis) is another example; it disrupts immune system signaling, contributing to prolonged infection.
Review Questions
- What are the roles of the A and B subunits in an A-B exotoxin?
- Which bacteria produce A-B exotoxins that affect the respiratory system?
- How do A-B exotoxins contribute to the pathogenicity of respiratory infections?
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Related terms
Exotoxin: Toxic proteins secreted by bacteria that can cause damage to host tissues.
Endotoxin: Lipopolysaccharides found in the outer membrane of Gram-negative bacteria that can trigger strong immune responses.
Respiratory Tract Infection: An infection affecting any part of the respiratory system, including upper and lower respiratory tracts.
