Mössbauer studies on the active Fe ... [2Fe-2S] site of putidamonooxin, its electron transport and dioxygen activation mechanism.
Putidamonooxin, the oxygenase of a 4-methoxybenzoate monooxygenase enzyme system, catalyzes the oxidative O-demethylation of the substrate 4-methoxybenzoate in conjunction with the NADH:putidamonooxin oxidoreductase. Putidamonooxin is a conjugated iron-sulfur protein which needs iron ions as cofactors for its enzymatic activity. Putiamonooxin was isolated from Pseudomonas putida, which was grown on a 57Fe-enriched culture medium. Thus putidamonooxin was enriched in vivo with 57Fe up to about 80%. During our Mössbauer study of putidamonooxin a number of parameters have been varied: (a) the oxidation state of putidamonooxin (oxidized, reduced and aerobically reoxidized); (b) the substrate bound to putidamonooxin (4-methoxybenzoate, benzoate, 4-tert-butylbenzoate); (c) the temperature between 2.7 K and 245 K; (d) the applied magnetic field between 0 and 0.1 T and (e) the amount of iron cofactor. From our Mössbauer results it is obvious that the iron-sulfur centers of putidamonooxin are [2 Fe-2S] clusters similar to those of the plant-type ferredoxins. Further, we have evidence for the existence of iron ions (one per [2 Fe-2S] cluster), which serve as cofactors for the dioxygen activation, functioning as the dioxygen binding site and mediating the electron flow from the [2 Fe-2S] cluster to dioxygen.
D001665:Binding Sites; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D007501:Iron / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010105:Oxygenases / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology; D013051:Spectrometry, Gamma; D013696:Temperature
D007506:Iron-Sulfur Proteins; D007501:Iron; D010105:Oxygenases; C022485:putidamonooxin; D010100:Oxygen