X-ray absorption spectroscopic characterization of the diferric-peroxo intermediate of human deoxyhypusine hydroxylase in the presence of its substrate eIF5a.
J Biol Inorg Chem
; 21(5-6): 605-18, 2016 09.
Article
em En
| MEDLINE
| ID: mdl-27380180
ABSTRACT
Human deoxyhypusine hydroxylase (hDOHH) is an enzyme that is involved in the critical post-translational modification of the eukaryotic translation initiation factor 5A (eIF5A). Following the conversion of a lysine residue on eIF5A to deoxyhypusine (Dhp) by deoxyhypusine synthase, hDOHH hydroxylates Dhp to yield the unusual amino acid residue hypusine (Hpu), a modification that is essential for eIF5A to promote peptide synthesis at the ribosome, among other functions. Purification of hDOHH overexpressed in E. coli affords enzyme that is blue in color, a feature that has been associated with the presence of a peroxo-bridged diiron(III) active site. To gain further insight into the nature of the diiron site and how it may change as hDOHH goes through the catalytic cycle, we have conducted X-ray absorption spectroscopic studies of hDOHH on five samples that represent different species along its reaction pathway. Structural analysis of each species has been carried out, starting with the reduced diferrous state, proceeding through its O2 adduct, and ending with a diferric decay product. Our results show that the Feâ¯Fe distances found for the five samples fall within a narrow range of 3.4-3.5 Å, suggesting that hDOHH has a fairly constrained active site. This pattern differs significantly from what has been associated with canonical dioxygen activating nonheme diiron enzymes, such as soluble methane monooxygenase and Class 1A ribonucleotide reductases, for which the Feâ¯Fe distance can change by as much as 1 Å during the redox cycle. These results suggest that the O2 activation mechanism for hDOHH deviates somewhat from that associated with the canonical nonheme diiron enzymes, opening the door to new mechanistic possibilities for this intriguing family of enzymes.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fatores de Iniciação de Peptídeos
/
Proteínas de Ligação a RNA
/
Oxigenases de Função Mista
Tipo de estudo:
Prognostic_studies
Limite:
Humans
Idioma:
En
Revista:
J Biol Inorg Chem
Assunto da revista:
BIOQUIMICA
Ano de publicação:
2016
Tipo de documento:
Article
País de afiliação:
Estados Unidos