title: EPR spectroscopic characterization of an 'iron only' nitrogenase. S = 3/2 spectrum of component 1 isolated from Rhodobacter capsulatus.
abstract: 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.
authors.affiliation: Fakultät für Chemie, Lehrstuhl für Anorganische Chemie I, Universität Bielefeld, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Müller
authors.forename: K
authors.initials: K
authors.lastname: Schneider
authors.forename: K
authors.initials: K
authors.lastname: Knüttel
authors.forename: W R
authors.initials: WR
authors.lastname: Hagen
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000378:metabolism*; D009591:Nitrogenase / Q000378:metabolism*; D016354:Rhodobacter capsulatus / Q000201:enzymology*
chemical_list: D007501:Iron; D009591:Nitrogenase