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Spectroscopic Evidence for Electronic Control of Heme Hydroxylation by IsdG.
Conger, Matthew A; Cornetta, Amanda R; Liptak, Matthew D.
Afiliación
  • Conger MA; Department of Chemistry , University of Vermont , Burlington , Vermont 05405 , United States.
  • Cornetta AR; Department of Chemistry , University of Vermont , Burlington , Vermont 05405 , United States.
  • Liptak MD; Department of Chemistry , University of Vermont , Burlington , Vermont 05405 , United States.
Inorg Chem ; 58(22): 15455-15465, 2019 Nov 18.
Article en En | MEDLINE | ID: mdl-31693363
Staphylococcus aureus IsdG catalyzes a unique trioxygenation of heme to staphylobilin, and the data presented in this article elucidate the mechanism of the novel chemical transformation. More specifically, the roles of the second-sphere Asn and Trp residues in the monooxygenation of ferric-peroxoheme have been clarified via spectroscopic characterization of the ferric-azidoheme analogue. Analysis of UV/vis absorption data quantified the strength of the hydrogen bond that exists between the Asn7 side chain and the azide moiety of ferric-azidoheme. X-band electron paramagnetic resonance data were acquired and analyzed, which revealed that this hydrogen bond weakens the π-donor strength of the azide, resulting in perturbations of the Fe 3d based orbitals. Finally, nuclear magnetic resonance characterization of 13C-enriched samples demonstrated that the Asn7···N3 hydrogen bond triggers partial porphyrin to iron electron transfer, resulting in spin density delocalization onto the heme meso carbons. These spectroscopic experiments were complemented by combined quantum mechanics/molecular mechanics computational modeling, which strongly suggested that the electronic structure changes observed for the N7A variant arose from loss of the Asn7···N3 hydrogen bond as opposed to a decrease in porphyrin ruffling. From these data a fascinating picture emerges where an Asn7···N3 hydrogen bond is communicated through four bonds, resulting in meso carbons with partial cationic radical character that are poised for hydroxylation. This chemistry is not observed in other heme proteins because Asn7 and Trp67 must work in concert to trigger the requisite electronic structure change.
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Idioma: En Revista: Inorg Chem Año: 2019 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos
Texto completo
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Idioma: En Revista: Inorg Chem Año: 2019 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos