學士後西醫-普通生物及生化概論題庫下載題庫

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.