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Fate of oxygen species from O-2 activation at dimetal cofactors in an oxidase enzyme revealed by Fe-57 nuclear resonance X-ray scattering and quantum chemistry
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
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Number of Authors: 62019 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1860, no 12, article id 148060Article in journal (Refereed) Published
Abstract [en]

Oxygen (O-2) activation is a central challenge in chemistry and catalyzed at prototypic dimetal cofactors in biological enzymes with diverse functions. Analysis of intermediates is required to elucidate the reaction paths of reductive O-2 cleavage. An oxidase protein from the bacterium Geobacillus kaustophilus, R2lox, was used for aerobic in-vitro reconstitution with only Fe-57(II) or Mn(II) plus Fe-57(II) ions to yield [FeFe] or [MnFe] cofactors under various oxygen and solvent isotopic conditions including O-16/18 and H/D exchange. Fe-57-specific X-ray scattering techniques were employed to collect nuclear forward scattering (NFS) and nuclear resonance vibrational spectroscopy (NRVS) data of the R2lox proteins. NFS revealed Fe/Mn(III)Fe(III) cofactor states and Mossbauer quadrupole splitting energies. Quantum chemical calculations of NRVS spectra assigned molecular structures, vibrational modes, and protonation patterns of the cofactors, featuring a terminal water (H2O) bound at iron or manganese in site 1 and a metal-bridging hydroxide (mu OH-) ligand. A procedure for quantitation and correlation of experimental and computational NRVS difference signals due to isotope labeling was developed. This approach revealed that the protons of the ligands as well as the terminal water at the R2lox cofactors exchange with the bulk solvent whereas O-18 from O-18(2) cleavage is incorporated in the hydroxide bridge. In R2lox, the two water molecules from four-electron O-2 reduction are released in a two-step reaction to the solvent. These results establish combined NRVS and QM/MM for tracking of iron-based oxygen activation in biological and chemical catalysts and clarify the reductive O-2 cleavage route in an enzyme.

Place, publisher, year, edition, pages
2019. Vol. 1860, no 12, article id 148060
Keywords [en]
Ferritin superfamily, Ligand-binding oxidase, Oxygen activation, Nuclear resonance X-ray scattering, Quantum chemistry, Isotope labeling
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:su:diva-178715DOI: 10.1016/j.bbabio.2019.148060ISI: 000504950800002PubMedID: 31394094OAI: oai:DiVA.org:su-178715DiVA, id: diva2:1391465
Available from: 2020-02-04 Created: 2020-02-04 Last updated: 2020-02-04Bibliographically approved

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Srinivas, VivekGriese, Julia J.Högbom, Martin
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