A-B exotoxins

Definition

A-B exotoxins are bacterial proteins consisting of two components: an 'A' (active) part that exerts toxic effects, and a 'B' (binding) part that facilitates entry into host cells. These toxins disrupt cellular processes, often leading to disease symptoms.

5 Must Know Facts For Your Next Test

1. A-B exotoxins are composed of two subunits: A (enzyme activity) and B (cell binding).
2. The B subunit binds to host cell receptors, allowing the A subunit to enter the cell.
3. Common examples include diphtheria toxin, cholera toxin, and botulinum toxin.
4. These toxins can interfere with protein synthesis or signal transduction pathways in host cells.
5. They are typically produced by Gram-positive bacteria but can also be found in some Gram-negative bacteria.

Review Questions

• What are the roles of the A and B subunits in A-B exotoxins?
• Name three diseases caused by bacteria producing A-B exotoxins.
• How do A-B exotoxins typically enter host cells?

Related terms

Endotoxin:

Toxic components of the outer membrane of certain Gram-negative bacteria released upon cell death.

Virulence Factor: Molecules produced by pathogens that contribute to their ability to cause disease.

Toxin-antitoxin system: A set of two or more closely linked genes encoding both a toxin and its corresponding antitoxin.