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Hypusine N epsilon-(4-amino-2-hydroxybutyl)lysine occurs in all eukaryotes at one residue in a highly conserved protein, the putative eukaryotic translation initiation factor 5A (eIF-5A, old terminology eIF-4D). This unusual amino acid is produced in a unique posttranslational modification reaction that involves the conjugation of the 4-aminobutyl moiety of the polyamine spermidine to the epsilon-amino group of a specific lysine residue of the eIF-5A precursor protein to form the deoxyhypusine N epsilon-(4-aminobutyl)lysine residue and its subsequent hydroxylation. The strict specificity of hypusine synthesis, its derivation from spermidine and its requirement for the activity of eIF-5A and for eukaryotic cell proliferation have raised keen interest in the physiological function of the hypusine-containing protein, eIF-5A.
Park et al. (Wed,) studied this question.