The critical role of tryptophan-116 in the catalytic cycle of dimethylsulfoxide reductase from Rhodobacter capsulatus.
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.
Ridge
Justin P
JP
Centre for Metals in Biology, School of Molecular and Microbial Sciences, University of Queensland, Brisbane, Qld. 4072, Australia.
Aguey-Zinsou
Kondo-Francois
KF
Bernhardt
Paul V
PV
Hanson
Graeme R
GR
McEwan
Alastair G
AG
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*
D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D008024:Ligands; D011522:Protons; D010649:Phenylalanine; D008982:Molybdenum; D014364:Tryptophan; D010088:Oxidoreductases; C045664:dimethyl sulfoxide reductase