Final answer:
A-B toxins have two subunits, A and B. The B subunit binds to host cell receptors, allowing the toxin to enter the cell. The A subunit interferes with specific cellular functions, often inhibiting protein synthesis or disrupting cellular processes. Examples of AB toxins include diphtheria toxin and cholera toxin.
Step-by-step explanation:
A-B toxins are a class of exotoxins that have two subunits, A and B. The B subunit is responsible for binding to specific receptors on host cells. Once the toxin binds to the cell, it is taken in by endocytosis, and the A and B subunits separate. The A subunit then enters the cell cytoplasm and interferes with specific cellular functions, often inhibiting protein synthesis or disrupting cellular processes.
For example, the diphtheria toxin inhibits protein synthesis in host cells by transferring adenosine diphosphate (ADP)-ribose onto an elongation-factor protein (EF-2).
The clinical relevance of AB toxins is significant as they can cause severe diseases. For instance, cholera toxin produced by Vibrio cholerae causes diarrhea by interfering with the normal functioning of intestinal cells.