title: The critical role of tryptophan-116 in the catalytic cycle of dimethylsulfoxide reductase from Rhodobacter capsulatus.
abstract: In dimethylsulfoxide reductase of Rhodobacter capsulatus tryptophan-116 forms a hydrogen bond with a single oxo ligand bound to the molybdenum ion. Mutation of this residue to phenylalanine affected the UV/visible spectrum of the purified Mo(VI) form of dimethylsulfoxide reductase resulting in the loss of the characteristic transition at 720 nm. Results of steady-state kinetic analysis and electrochemical studies suggest that tryptophan 116 plays a critical role in stabilizing the hexacoordinate monooxo Mo(VI) form of the enzyme and prevents the formation of a dioxo pentacoordinate Mo(VI) species, generated as a consequence of the dissociation of one of the dithiolene ligands of the molybdopterin cofactor from the Mo ion.
authors.affiliation: Centre for Metals in Biology, School of Molecular and Microbial Sciences, University of Queensland, Brisbane, Qld. 4072, Australia.
authors.forename: Justin P
authors.initials: JP
authors.lastname: Ridge
authors.forename: Kondo-Francois
authors.initials: KF
authors.lastname: Aguey-Zinsou
authors.forename: Paul V
authors.initials: PV
authors.lastname: Bernhardt
authors.forename: Graeme R
authors.initials: GR
authors.lastname: Hanson
authors.forename: Alastair G
authors.initials: AG
authors.lastname: McEwan
mesh_terms: D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000378:metabolism*; D002384:Catalysis; D004563:Electrochemistry; D006860:Hydrogen Bonding; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry*; D016297:Mutagenesis, Site-Directed; D010088:Oxidoreductases / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism; D011522:Protons; D016354:Rhodobacter capsulatus / Q000201:enzymology* / Q000302:isolation & purification; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D008024:Ligands; D011522:Protons; D010649:Phenylalanine; D008982:Molybdenum; D014364:Tryptophan; D010088:Oxidoreductases; C045664:dimethyl sulfoxide reductase