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

1. A-B exotoxins are produced by bacteria such as Corynebacterium diphtheriae and Bordetella pertussis, both of which cause serious respiratory infections.
2. The A subunit typically interferes with internal cellular processes by modifying host cell proteins or signaling pathways.
3. The B subunit determines the specificity of the toxin for particular cell types by binding to specific receptors on the host cell surface.
4. Diphtheria toxin (produced by Corynebacterium diphtheriae) is an example of an A-B exotoxin that inhibits protein synthesis in host cells.
5. 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?

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.