Fate of oxygen species from O2 activation at dimetal cofactors in an oxidase enzyme revealed by 57Fe nuclear resonance X-ray scattering and quantum chemistry

Publication date: Available online 5 August 2019Source: Biochimica et Biophysica Acta (BBA) - BioenergeticsAuthor(s): Stefan Mebs, Vivek Srinivas, Ramona Kositzki, Julia J. Griese, Martin Högbom, Michael HaumannAbstractOxygen (O2) 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 O2 cleavage. An oxidase protein from the bacterium Geobacillus kaustophilus, R2lox, was used for aerobic in-vitro reconstitution with only 57Fe(II) or Mn(II) plus 57Fe(II) ions to yield [FeFe] or [MnFe] cofactors under various oxygen and solvent isotopic conditions including 16/18O and H/D exchange. 57Fe-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 Mössbauer 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 (μOH−) 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 ...
Source: Biochimica et Biophysica Acta (BBA) Bioenergetics - Category: Biochemistry Source Type: research