Exchangeable oxygens in the vicinity of the molybdenum center of the high-pH form of sulfite oxidase and sulfite dehydrogenase

Andrei V. Astashkin, Eric L. Klein, Dmitry Ganyushin, Kayunta Johnson-Winters, Frank Neese, Ulrike Kappler, John H. Enemark

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23 Scopus citations

Abstract

The electron spin echo envelope modulation (ESEEM) investigation of the high-pH (hpH) form of sulfite oxidase (SO) and sulfite dehydrogenase (SDH) prepared in buffer enriched with H217O reveals the presence of three types of exchangeable oxygen atoms at the molybdenum center. Two of these oxygen atoms belong to the equatorial OH ligand and the axial oxo ligand, and are characterized by 17O hyperfine interaction (hfi) constants of about 37 MHz and 6 MHz, respectively. The third oxygen has an isotropic hfi constant of 3-4 MHz and likely belongs to a hydroxyl moiety hydrogen-bonded to the equatorial OH ligand. This exchangeable oxygen atom is not observed in the ESEEM spectra of the Y236F mutant of SDH, where the active site tyrosine has been replaced by phenylalanine.

Original languageEnglish
Pages (from-to)6733-6742
Number of pages10
JournalPhysical Chemistry Chemical Physics
Volume11
Issue number31
DOIs
StatePublished - 2009
Externally publishedYes

Funding

FundersFunder number
National Center for Research ResourcesS10RR020959

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