Redox properties and electron paramagnetic resonance spectroscopy of the transition state complex of Azotobacter vinelandii nitrogenase.
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.
Spee
J H
JH
Department of Biomolecular Sciences, Agricultural University, Wageningen, The Netherlands.
Arendsen
A F
AF
Wassink
H
H
Marritt
S J
SJ
Hagen
W R
WR
Haaker
H
H
D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000737:chemistry*; D017607:Aluminum Compounds / Q000494:pharmacology; D016948:Azotobacter vinelandii / Q000201:enzymology*; D004578:Electron Spin Resonance Spectroscopy; D005459:Fluorides / Q000494:pharmacology; D006868:Hydrolysis; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D008667:Metalloproteins / Q000737:chemistry*; D008982:Molybdenum / Q000737:chemistry; D009591:Nitrogenase / Q000737:chemistry*; D010084:Oxidation-Reduction; D011199:Potentiometry; D011487:Protein Conformation
D017607:Aluminum Compounds; D007506:Iron-Sulfur Proteins; D008667:Metalloproteins; D000244:Adenosine Diphosphate; D008982:Molybdenum; D009591:Nitrogenase; D000251:Adenosine Triphosphatases; D005459:Fluorides; C032311:aluminum fluoride