Mössbauer spectroscopy applied to the oxidized and semi-reduced states of the iron-molybdenum cofactor of nitrogenase

• Published in: Biochemical and biophysical research communications Vol. 162; no. 2; pp. 882 - 891
• Main Authors: Newton, William E., Gheller, Stephen F., Sands, Richard H., Dunham, W.R.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 31.07.1989; Elsevier
• Subjects: Analytical, structural and metabolic biochemistry; Azotobacter - enzymology; Azotobacter vinelandii; Biological and medical sciences; Enzymes and enzyme inhibitors; Ferredoxins - analysis; Fundamental and applied biological sciences. Psychology; iron; Iron - analysis; molybdenum; Molybdenum - analysis; Molybdoferredoxin - analysis; Nitrogenase - analysis; Oxidation-Reduction; Oxidoreductases; Spectroscopy, Mossbauer; red; MoFe protein; NMF; EPR; EFG; ox; s-r; FeMoco; XAS; ENDOR; Azotobacteraceae; Enzyme; Nitrogenase; Bacteria; Oxidation number; Iron; Moessbauer spectrometry; Azotobacter vinelandii; Cofactor; Molybdenum
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/0006-291X(89)92392-9

Mössbauer parameters at 125K for both the oxidized and semi-reduced states of FeMoco isolated from the MoFe protein of Azotobacter vinelandii nitrogenase of δ Fe =0.32 and 0.37 mm/s and ΔEq=0.84 and 0.71 mm/s, respectively, are reported. FeMoco(ox) fits the Debye model perfectly from 4.2–125K and has a S=0 ground state. FeMoco(ox) apparently contains 10–20% FeMoco(s-r) and vice versa , possibly as a result of the spontaneous oxidation phenomenon. Quantitation of the spectra indicates a Fe:Mo ratio of 5±1:1 and the similar quadrupole splittings and isomer shifts suggest a similar environment for all iron atoms.