1. Redox properties and electron paramagnetic resonance spectroscopy of the transition state complex of Azotobacter vinelandii nitrogenase.
- Author
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Spee JH, Arendsen AF, Wassink H, Marritt SJ, Hagen WR, and Haaker H
- Subjects
- Adenosine Diphosphate metabolism, Aluminum Compounds pharmacology, Electron Spin Resonance Spectroscopy, Fluorides pharmacology, Hydrolysis, Iron-Sulfur Proteins chemistry, Molybdenum chemistry, Oxidation-Reduction, Potentiometry, Protein Conformation, Adenosine Triphosphatases chemistry, Azotobacter vinelandii enzymology, Metalloproteins chemistry, Nitrogenase chemistry
- Abstract
Nitrogenase is a two-component metalloenzyme that catalyzes a MgATP hydrolysis driven reduction of substrates. Aluminum fluoride plus MgADP inhibits nitrogenase by stabilizing an intermediate of the on-enzyme MgATP hydrolysis reaction. We report here the redox properties and electron paramagnetic resonance (EPR) signals of the aluminum fluoride-MgADP stabilized nitrogenase complex of Azotobacter vinelandii. Complex formation lowers the midpoint potential of the [4Fe-4S] cluster in the Fe protein. Also, the two-electron reaction of the unique [8Fe-7S] cluster in the MoFe protein is split in two one-electron reactions both with lower midpoint potentials. Furthermore, a change in spin-state of the two-electron oxidized [8Fe-7S] cluster is observed. The implications of these findings for the mechanism of MgATP hydrolysis driven electron transport within the nitrogenase protein complex are discussed.
- Published
- 1998
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