Diphtheria toxin and exotoxin A are well-characterized members of the 
ADP-ribosyltransferase toxin family that function as virulence factors in the 
pathogenic bacteria Corynebacterium diphtheriae and Pseudomonas aeruginosa. 
Recent high-resolution structural data of the Michaelis (enzyme-substrate) 
complex of the P. aeruginosa toxin with an NAD(+) analog and eukaryotic 
elongation factor 2 (eEF2) have provided insights into the mechanism of 
inactivation of protein synthesis caused by these protein factors. In addition, 
rigorous steady-state and stopped-flow kinetic analyses of the toxin-catalyzed 
reaction, in combination with inhibitor studies, have resulted in a quantum leap 
in our understanding of the mechanistic details of this deadly enzyme mechanism. 
It is now apparent that these toxins use stealth and molecular mimicry in 
unleashing their toxic strategy in the infected host eukaryotic cell.