Jh. Spee et al., REDOX PROPERTIES AND ELECTRON-PARAMAGNETIC-RESONANCE SPECTROSCOPY OF THE TRANSITION-STATE COMPLEX OF AZOTOBACTER-VINELANDII NITROGENASE, FEBS letters, 432(1-2), 1998, pp. 55-58
Nitrogenase is a two-component metalloenzyme that catalyzes a MgATP hy
drolysis driven reduction of substrates, Aluminum fluoride plus MgADP
inhibits nitrogenase by stabilizing an intermediate of the on-enzyme M
gATP hydrolysis reaction. We report here the redox properties and elec
tron paramagnetic resonance (EPR) signals of the aluminum fluoride-MgA
DP stabilized nitrogenase complex of Azotobacter vinelandii. Complex f
ormation lowers the midpoint potential of the [4Fe-4S] cluster in the
Fe protein. Also, the two-electron reaction of the unique [8Fe-7S] clu
ster in the MoFe protein is split in two one-electron reactions both w
ith loner midpoint potentials. Furthermore, a change in spin-state of
the tno-electron oxidized [8Fe-7S] cluster is observed. The implicatio
ns of these findings for the mechanism of MgATP hydrolysis driven elec
tron transport within the nitrogenase protein complex are discussed. (
C) 1998 Federation of European Biochemical Societies.