58. The bacterium Corynebacterium diphtheriae produces a potent toxin to block host cell translation. Which of the following descriptions is NOT a property of diphtheria toxin? (A) The toxin modifies a histidine residue on ¢EF-2 to form diphthamide. (B) The toxin catalyzes an ADP-ribosylation reaction on eEF-2. (C) One of the substrates of the toxin is NAD", and one nicotinamide is released in the reaction. (D) The modified eEF-2 retains the ability to bind GTP but cannot function in protein synthesis. (E) One toxin can catalytically modify many eEF-2 molecules.