Resonance Raman characterization of biotin sulfoxide reductase. Comparing oxomolybdenum enzymes in the ME(2)SO reductase family.

Published

Journal Article

Resonance Raman spectroscopy has been used to define active site structures for oxidized Mo(VI) and reduced Mo(IV) forms of recombinant Rhodobacter sphaeroides biotin sulfoxide reductase expressed in Escherichia coli. On the basis of (18)O/(16)O labeling studies involving water and the alternative substrate dimethyl sulfoxide and the close correspondence to the resonance Raman spectra previously reported for dimethyl sulfoxide reductase (Garton, S. D., Hilton, J., Oku, H., Crouse, B. R., Rajagopalan, K. V., and Johnson, M. K. (1997) J. Am. Chem. Soc. 119, 12906-12916), vibrational modes associated with a terminal oxo ligand and the two molybdopterin dithiolene ligands have been assigned. The results indicate that the enzyme cycles between mono-oxo-Mo(VI) and des-oxo-Mo(IV) forms with both molybdopterin dithiolene ligands remaining coordinated in both redox states. Direct evidence for an oxygen atom transfer mechanism is provided by (18)O/(16)O labeling studies, which show that the terminal oxo group at the molybdenum center is exchangeable with water during redox cycling and originates from the substrate in substrate-oxidized samples. Biotin sulfoxide reductase is not reduced by biotin or the nonphysiological products, dimethyl sulfide and trimethylamine. However, product-induced changes in the Mo=O stretching frequency provide direct evidence for a product-associated mono-oxo-Mo(VI) catalytic intermediate. The results indicate that biotin sulfoxide reductase is thermodynamically tuned to catalyze the reductase reaction, and a detailed catalytic mechanism is proposed.

Full Text

Duke Authors

Cited Authors

  • Garton, SD; Temple, CA; Dhawan, IK; Barber, MJ; Rajagopalan, KV; Johnson, MK

Published Date

  • March 10, 2000

Published In

Volume / Issue

  • 275 / 10

Start / End Page

  • 6798 - 6805

PubMed ID

  • 10702237

Pubmed Central ID

  • 10702237

International Standard Serial Number (ISSN)

  • 0021-9258

Digital Object Identifier (DOI)

  • 10.1074/jbc.275.10.6798

Language

  • eng

Conference Location

  • United States