The mechanism of action of the exotoxin produced by Corynebacterium diphtheriae can be characterized by which of the following?
**Core Concept**
The exotoxin produced by Corynebacterium diphtheriae is a potent neurotoxin that inhibits protein synthesis in host cells. This toxin is responsible for the severe manifestations of diphtheria, including cardiac and neurological complications.
**Why the Correct Answer is Right**
The exotoxin, known as diphtheria toxin (DT), acts by inactivating the elongation factor-2 (EF-2) through ADP-ribosylation. This process prevents the translocation of peptidyl-tRNA from the A site to the P site on the ribosome, thereby inhibiting protein synthesis. The toxin is produced in the bacterial cytoplasm and is secreted into the surrounding tissue, where it can cause widespread damage.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not related to the mechanism of action of diphtheria toxin.
* **Option B:** While diphtheria toxin does cause cell death, its primary mechanism is through inhibition of protein synthesis, not through induction of apoptosis.
* **Option C:** Diphtheria toxin does not act by inhibiting the production of cAMP.
**Clinical Pearl / High-Yield Fact**
The diphtheria toxin is a classic example of a bacterial exotoxin that causes significant morbidity and mortality. The development of toxoid vaccines has been instrumental in controlling the spread of diphtheria, highlighting the importance of immunoprophylaxis in preventing infectious diseases.
**Correct Answer: C. Inhibition of protein synthesis through ADP-ribosylation of elongation factor-2.**