This modification has been extensively studied because it is targeted by the diphtheria toxin which is a potent exotoxin produced by Corynebacterium diphtheriae leading to the ADP-ribosylation of the eEF2 protein at the diphthamide residue causing diphtheria and upper respiratory tract infection (Schaffrath et al. 2014). The gene discussed is EEF2; the disease is Recurrent upper respiratory tract infections.