Question

One potential cancer therapy is to remodel an AB-type exotoxin in order to target the toxin specifically to cancer and kill them. Describe how you would modify the exotoxin to achieve this. In your answer, include a description of the function of the A and B subunit.

Answer 1

Many pathogenic bacteria produce exotoxins and secrete in the surrounding environment or release after lysis. Exotoxins are protein in nature that has the ability to kill the infected cell by interfering with normal cellular metabolism as well as signaling pathways. AB- exotoxins are Type III toxins that act inside the cell. In AB- exotoxins, A-subunit is the Active component having enzymatic activity and B-subunit is the Binding component that binds the exotoxin to the host cell. AB-type exotoxin is recognized as a potent immunotoxin that has the capability to bind specifically to target cancer cells and kill them. Cancer cells have unique receptors that normal cells do not have. The B subunit of AB-type exotoxin is responsible for the binding of A subunit to a receptor present on the surface of the target cell. So, the toxin can be targeted specifically to the cancer cells if the B subunit is modified such a way that it will bind the exotoxin to the receptors only present on the cancer cells.