EPR spectroscopic characterization of an ‘iron only⌉ nitrogenase S = 3/2 spectrum of component 1 isolated from Rhodobacter capsulatus
- 25 May 1992
- journal article
- Published by Wiley in FEBS Letters
- Vol. 303 (1) , 36-40
- https://doi.org/10.1016/0014-5793(92)80472-s
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’) or this enzyme showed an EPR spectrum consisting of two components: a minor S = 12 signal at g = 1.93 and a very characteristic S = 32 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 = 32 system or 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.Keywords
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