title: The post-translational synthesis of a polyamine-derived amino acid, hypusine, in the eukaryotic translation initiation factor 5A (eIF5A).
abstract: The eukaryotic translation initiation factor 5A (eIF5A) is the only cellular protein that contains the unique polyamine-derived amino acid, hypusine [Nepsilon-(4-amino-2-hydroxybutyl)lysine]. Hypusine is formed in eIF5A by a novel post-translational modification reaction that involves two enzymatic steps. In the first step, deoxyhypusine synthase catalyzes the cleavage of the polyamine spermidine and transfer of its 4-aminobutyl moiety to the epsilon-amino group of one specific lysine residue of the eIF5A precursor to form a deoxyhypusine intermediate. In the second step, deoxyhypusine hydroxylase converts the deoxyhypusine-containing intermediate to the hypusine-containing mature eIF5A. The structure and mechanism of deoxyhypusine synthase have been extensively characterized. Deoxyhypusine hydroxylase is a HEAT-repeat protein with a symmetrical superhelical structure consisting of 8 helical hairpins (HEAT motifs). It is a novel metalloenzyme containing tightly bound iron at the active sites. Four strictly conserved His-Glu pairs were identified as iron coordination sites. The structural fold of deoxyhypusine hydroxylase is entirely different from those of the other known protein hydroxylases such as prolyl 4-hydroxylase and lysyl hydroxylases. The eIF5A protein and deoxyhypusine/hypusine modification are essential for eukaryotic cell proliferation. Thus, hypusine synthesis represents the most specific protein modification known to date, and presents a novel target for intervention in mammalian cell proliferation.
authors.affiliation: The Oral and Pharyngeal Cancer Branch, NIDCR, National Institutes of Health, Bethesda, MD 20892-4340, USA. mhpark@nih.gov
authors.forename: Myung Hee
authors.initials: MH
authors.lastname: Park
mesh_terms: D000818:Animals; D002384:Catalysis; D006801:Humans; D008239:Lysine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000378:metabolism; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000737:chemistry / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000737:chemistry / Q000378:metabolism*; D011073:Polyamines / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D000097574:Eukaryotic Translation Initiation Factor 5A
chemical_list: D008239:Lysine; D006899:Mixed Function Oxygenases; D000587:Oxidoreductases Acting on CH-NH Group Donors; D010448:Peptide Initiation Factors; D011073:Polyamines; D016601:RNA-Binding Proteins; D000097574:Eukaryotic Translation Initiation Factor 5A; C100028:hypusine; C047991:deoxyhypusine hydroxylase; C063507:deoxyhypusine synthase