Klebsiella pneumoniae nitrogenase: pre-steady-state absorbance changes show that redox changes occur in the MoFe protein that depend on substrate and component protein ratio; a role for P-centres in reducing dinitrogen?
The pre-steady-state absorbance changes that occur during the first 0.6 s of reaction of the nitrogenase of Klebsiella pneumoniae can be simulated by associating redox changes with the different states of the MoFe protein described by our published kinetic model for nitrogenase [Lowe and Thorneley (1984) Biochem. J. 224, 877-886]. When the substrate is changed, from H+ to C2H2 (acetylene) or N2, or the nitrogenase component protein ratio is altered, these pre-steady-state absorbance changes are affected in a manner that is quantitatively predicted by our model. The results, together with parallel e.p.r. studies, are interpreted as showing that the P-clusters become oxidized when the MoFe protein is in the state where bound N2 is irreversibly committed to being reduced and is protonated to the hydrazido(2-) level.
AFRC Institute of Plant Science Research, Nitrogen Fixation Laboratory, University of Sussex, Brighton, U.K.
D J
DJ
Lowe
K
K
Fisher
R N
RN
Thorneley
D004578:Electron Spin Resonance Spectroscopy; D007711:Klebsiella pneumoniae / Q000201:enzymology*; D008983:Molybdoferredoxin / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D009591:Nitrogenase / Q000737:chemistry*; D010084:Oxidation-Reduction; D013057:Spectrum Analysis; D013379:Substrate Specificity
D008983:Molybdoferredoxin; D009591:Nitrogenase; D009584:Nitrogen