DITHIOTHREITOL GENERATES AN ACTIVATED 250,000 MOL WT FORM OF CLOSTRIDIUM-DIFFICILE TOXIN-B

The potent cytotoxin of Clostridium difficile, toxin B, is internalize d by endocytosis and activated intracellularly by an unidentified mech anism. Here it is shown that dithiothreitol treatment of toxin B resul ted in (1) a mol. wt of 250,000 which is the smallest species of this toxin shown to be cytotoxic; (2) an increased endpoint titre; and (3) translocation of plasma membrane-bound toxin across the membrane at pH 4.5. Treatment with dithiothreitol can thus mimic intracellular activ ation of the toxin. Radiolabelling of highly purified toxin with retai ned activity, as well as the 32 N-terminal amino acids and the amino a cid composition, is also presented.