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Electrochemical titration of the S = 3/2 and S = ½ states of the iron protein of nitrogenase
Author(s) -
Morgan T.Vance,
Prince Roger C.,
Mortenson Leonard E.
Publication year - 1986
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(86)81329-1
Subject(s) - nitrogenase , redox , redox titration , chemistry , molybdenum , spin states , electron paramagnetic resonance , titration , spin (aerodynamics) , inorganic chemistry , oxidation state , site directed spin labeling , sulfur , crystallography , biochemistry , nitrogen fixation , nuclear magnetic resonance , catalysis , nitrogen , physics , organic chemistry , thermodynamics , membrane
The iron protein of nitrogenase delivers electrons and ATP to the iron‐molybdenum protein, which in turn reduces dinitrogen to ammonia. The iron protein contains a single four‐iron, four‐sulfur prosthetic group, detectable by ESR spectroscopy m its reduced form. Until recently, spin quantitations suggested that only a portion of the reduced iron protein was being detected by ESR, but recent work in several laboratories has shown that there is a spin =signal near g = 5 in addition to the well characterized spin =signal near g = 1.94. In this paper we characterize the redox properties of both states in the presence and absence of ATP and ADP, and find that the new spin state has identical redox properties to those previously determined for the spin =state.