Crystal Structure of the Peroxo-diiron(III) Intermediate of Deoxyhypusine Hydroxylase, an Oxygenase Involved in Hypusination

Deoxyhypusine hydroxylase (DOHH) is a non-heme diiron enzyme involved in the posttranslational modification of a critical lysine residue of eukaryotic translation initiation factor 5A (eIF-5A) to yield the unusual amino acid residue hypusine. This modification is essential for the role of eIF-5A in translation and in nuclear export of a group of specific mRNAs. The diiron center of human DOHH (hDOHH) forms a peroxo-diiron(III) intermediate (hDOHH(peroxo)) when its reduced form reacts with O-2. hDOHH(peroxo) has a lifetime exceeding that of the peroxo intermediates of other diiron enzymes by several orders of magnitude. Here we report the 1.7-angstrom crystal structures of hDOHH(peroxo) and a complex with glycerol. The structure of hDOHH(peroxo) reveals the presence of a mu-1,2-peroxo-diiron(III) species at the active site. Augmented by UV/Vis and Mossbauer spectroscopic studies, the crystal structures offer explanations for the extreme longevity of hDOHH(peroxo) and illustrate how the enzyme specifically recognizes its only substrate, deoxyhypusine-eIF-5A.