EPR spectroscopic characterization of an 'iron only' nitrogenase. S = 3/2 spectrum of component 1 isolated from Rhodobacter capsulatus.
The alternative nitrogenase of Rhodobacter capsulatus, isolated from a nifHDK deletion mutant, has been purified to near homogeneity and identified as an 'iron only' nitrogenase. The dithionite-reduced component 1 ('FeFe protein') of this enzyme showed an EPR spectrum consisting of two components: a minor S = 1/2 signal at g = 1.93 and a very characteristic S = 3/2 signal of near-stoichiometric intensity at g = 5.44. This resonance is very close to the highest possible g value (g = 5.46) for the coinciding two intradoublet subspectra of an S = 3/2 system of maximal rhombicity (E/D = 0.33). The deviation from axial symmetry (increasing E/D) correlates with the stability, activity and substrate selectivity of the different (Mo, V, Fe) nitrogenases.
Müller
A
A
Fakultät für Chemie, Lehrstuhl für Anorganische Chemie I, Universität Bielefeld, Germany.
Schneider
K
K
Knüttel
K
K
Hagen
W R
WR
D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000378:metabolism*; D009591:Nitrogenase / Q000378:metabolism*; D016354:Rhodobacter capsulatus / Q000201:enzymology*
D007501:Iron; D009591:Nitrogenase