title: X-ray absorption spectroscopic characterization of the molybdenum site of Escherichia coli dimethyl sulfoxide reductase.
abstract: Structural studies of dimethyl sulfoxide (DMSO) reductases were hampered by modification of the active site during purification. We report an X-ray absorption spectroscopic analysis of the molybdenum active site of Escherichia coli DMSO reductase contained within its native membranes. The enzyme in these preparations is expected to be very close to the form found in vivo. The oxidized active site was found to have four Mo-S ligands at 2.43 A, one Mo=O at 1.71 A, and a longer Mo-O at 1.90 A. We conclude that the oxidized enzyme is a monooxomolybdenum(VI) species coordinated by two molybdopterin dithiolenes and a serine. The bond lengths determined for E. coli DMSO reductase are very similar to those determined for the well-characterized Rhodobacter sphaeroides DMSO reductase, suggesting similar active site structures for the two enzymes. Furthermore, our results suggest that the form found in vivo is the monooxobis(molybdopterin) species.
authors.affiliation: Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada. g.george@usask.ca
authors.forename: Graham N
authors.initials: GN
authors.lastname: George
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Doonan
authors.forename: Richard A
authors.initials: RA
authors.lastname: Rothery
authors.forename: Nasim
authors.initials: N
authors.lastname: Boroumand
authors.forename: Joel H
authors.initials: JH
authors.lastname: Weiner
mesh_terms: D001665:Binding Sites; D004926:Escherichia coli / Q000201:enzymology*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry*; D010088:Oxidoreductases / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D014965:X-Rays
chemical_list: D007506:Iron-Sulfur Proteins; D008982:Molybdenum; D010088:Oxidoreductases; C045664:dimethyl sulfoxide reductase