This model represents archaeal elongation factor 2, a protein more similar to eukaryotic EF-2 than to bacterial EF-G, both in sequence similarity and in sharing with eukaryotes the property of having a diphthamide (modified His) residue at a conserved position. The diphthamide can be ADP-ribosylated by diphtheria toxin in the presence of NAD. [Protein synthesis, Translation factors]