Diphtheria toxin induces leakage of acidic liposome

Diphtheria toxin (DT) induces the leakage of dipalmitoylphosphatidic acid (DPPA) membranes but not neutral dipalmitoylphosphatidylcholine (DPPC) membranes. Cholesterol incorporated into liposomes enhances the membrane leakage induced by DT in acidic DPPA membranes but not in neutral DPPC membranes. Membrane leakage was determined by assaying the release of TEMPOcholine, a cationic spin probe from the multilamellar vesicles by using electron spin resonance methods. The effect of DT on membrane leakage is noticeable at 3 μg/ml concentrations, and reaches a plateau of about 20% leakage at 20 μg/ml. This sauration phenomenon led to the postulation that DT binds to the first shell of DPPA membranes and induces the leakage of TEMPOcholine limited to this layer of DPPA multilamellar vesicles. © 1984.