Diphtheria toxin

Diphtheria toxin is produced by pathogenic strains of Corynebacterium diphtheriae. It acts catalytically on elongation factor 2 (EF-2), the eukaryotic homologue of EF-G. All EF-2s contain a postranslationally modified histidine residue called diphthamide. The toxin transfers ADP ribose from NAD+ to the imidazole ring. This completely inhibits translocation.