Which characteristic applies to the toxin produced by C. diphtheriae

Corynebacterium diphtheriae secretes a protein of approximately 62,000 molecular weight that exhibits toxicity against mammalian cells. Therefore, it is called an exotoxin (i.e., a toxic protein that is secreted by bacterial cells). It is a single polypeptide chain held together by two disulfide bridges. Fragment A exhibits enzymatic activity, resulting in permanent inactivation of elongation factor 2 (EF-2), whereas fragment B binds to cells and mediates entry of the toxic poion. The diphtheria toxin binds to epithelial cells of the pharynx and initially produces local damage. However, the toxin is absorbed into the body and blood circulation (toxemia) and can induce deleterious effects distant from its site of production. Paralysis of the soft palate, pharynx, larynx, and respiratory muscles may appear weeks after onset of symptoms. The toxin may also cause myocarditis. Electrocardiography abnormalities correlate with the level of toxemia. In rare cases, hypotension, peripheral circulatory failure, and skin hemorrhages may occur. Ref : Ananthanarayana textbook of Microbiology 9th edition Pgno : 236