Spectroscopic evidence for a high-spin Br-Fe(IV)-OxO intermediate in the α-ketoglutarate-dependent halogenase CytC3 from Streptomyces

Danica Galonić Fujimori, Eric W. Barr, Megan L. Matthews, Gretchen M. Koch, J. Ryan Yonce, Christopher T. Walsh, J. Martin Bollinger, Carsten Krebs, Pamela J. Riggs-Gelasco

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The complex of the mononuclear non-heme halogenase CytC3 from Streptomyces, Fe(II), α-ketoglutarate, bromide, and the substrate l-2-aminobutyryl-S-CytC2 reacts with O2 to form a reaction intermediate. Variable-field, freeze-quench Mössbauer spectroscopy reveals this intermediate to be a mixture of two high-spin Fe(IV) complexes in an approximate 3.7/1 ratio. Freeze-quench Fe K-edge X-ray absorption spectroscopy provides further insight into the structure of this intermediate. A short 1.62-Å interaction between the Fe and one of its ligands is attributed to the Fe(IV)-oxo group, and a 2.43-Å interaction is assigned to the Fe-Br interaction. A significantly longer Fe-Br separation (2.53 Å) is observed in the reactant complex, consistent with lower valency of the Fe in the reactant complex. This intermediate is the first example for a Br-Fe(IV)-oxo complex in a protein and provides evidence for a unifying mechanism for Fe(II) and α-ketoglutarate-dependent dioxygenases and halogenases.

Original languageEnglish (US)
Pages (from-to)13408-13409
Number of pages2
JournalJournal of the American Chemical Society
Issue number44
StatePublished - Nov 7 2007


All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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