Mechanism of action of diphtheria toxin -

Ans. is 'a' i.e., ADP ribosylation IMPORTANT BACTERIAL TOXINSToxinsMechanism of actionBotulinum toxin* Acts on the peripheral nervous system (i.e. neuromuscular junctions) by inhibiting myoneural junction acetylcholine release and cause flaccid paralysis (many strains of Clostridium botulinum synthesized C2 toxin, that ADP-ribosylates actin, thereby inhibiting its polymerization, affecting the shape of target cells, and resulting in enterotoxin activity in vivo).Diphtheria toxin* Inhibits protein synthesis in target cells by catalyzing the ADP ribosylation of a novel amino acid (diphthamide) on elongation factor 2, a host protein required for translocation of ribosomal messenger RNA.Pertussis toxin* Acts by ADP ribosylation of several members of the family of guanine nucleotide-binding (G) proteins involved in signal transduction, inhibiting their function and affecting a variety of effector systems, such as adenylate cyclase, phospholipases, and several types of ion channels.ST of E. coli* Activates guanylyl cyclase to increase cGMP.V. cholerae toxin LT of E. coli* Activates adenylate cyclase of the intestinal epithelial cell by AD ribosylation of the stimulatory G. protein, Gs -|cAMP.Shiga toxin* Inhibits protein synthesis by enzymatic inactivation of the28S RNA within the 60S ribosomal subunit.Verocytotoxin of E. coli toxin)* Inhibit protein synthesis by inhibiting ribosomal function (same as shiga