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EPR spectroscopic characterization of an ‘iron only⌉ nitrogenase S = 3/2 spectrum of component 1 isolated from Rhodobacter capsulatus
Author(s) -
Müller Achim,
Schneider Klaus,
Knüttel Karlheinz,
Hagen Wilfred R.
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80472-s
Subject(s) - rhodobacter , nitrogenase , electron paramagnetic resonance , chemistry , component (thermodynamics) , rhodospirillales , characterization (materials science) , spectrum (functional analysis) , rhodospirillaceae , stereochemistry , biochemistry , nitrogen fixation , photosynthesis , physics , materials science , nuclear magnetic resonance , organic chemistry , mutant , nanotechnology , nitrogen , gene , quantum mechanics , thermodynamics
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.