Structure of the active site of sulfite oxidase. X-ray absorption spectroscopy of the Mo(IV), Mo(V), and Mo(VI) oxidation states.
The active site of sulfite oxidase has been investigated by X-ray absorption spectroscopy at the molybdenum K-edge at 4 K. We have investigated all three accessible molybdenum oxidation states, Mo(IV), Mo(V), and Mo(VI), allowing comparison with the Mo(V) electron paramagnetic resonance data for the first time. Quantitative analysis of the extended X-ray absorption fine structure indicates that the Mo(VI) oxidation state possesses two terminal oxo (Mo = O) and approximately three thiolate-like (Mo-S-) ligands and is unaffected by changes in pH and chloride concentration. The Mo(IV) and Mo(V) oxidation states, however, each have a single oxo ligand plus one Mo-O- (or Mo-N less than) bond, most probably Mo--OH, and two to three thiolate-like ligands. Both reduced forms appear to gain a single chloride ligand under conditions of low pH and high chloride concentration.
George
G N
GN
Exxon Research and Engineering Company, Annandale, New Jersey 08801.
Kipke
C A
CA
Prince
R C
RC
Sunde
R A
RA
Enemark
J H
JH
Cramer
S P
SP
D000818:Animals; D001665:Binding Sites; D002645:Chickens; D004578:Electron Spin Resonance Spectroscopy; D004735:Energy Transfer; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D008982:Molybdenum / Q000032:analysis* / Q000494:pharmacology; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000032:analysis*; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000032:analysis*
D008982:Molybdenum; D010088:Oxidoreductases; D050862:Oxidoreductases Acting on Sulfur Group Donors