Open AccessElicitation of thiomolybdates from the iron‐molybdenum cofactor of nitrogenase
Author(s) -
NEWTON William E.,
GHELLER Stephen F.,
HEDMAN Britt,
HODGSON Keith O.,
LOUGH Samuel M.,
McDONALD John W.
Publication year - 1986
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1986.tb09839.x
Subject(s) - chemistry , azotobacter vinelandii , molybdenum , sodium dithionite , nitrogenase , ferrous , methanol , cofactor , inorganic chemistry , flammulina , dithionite , organic chemistry , nitrogen fixation , nitrogen , enzyme , mushroom , food science
Aerial oxidation of the iron‐molybdenum cofactor (FeMoco) of Azotobacter vinelandii nitrogenase has been shown to yield either the tetrathiomolybdate ion ([MoS 4 ] 2− ) or the oxotrithiomolybdate ion ([MoOS 3 ] 2− ), depending on the reaction conditions. Thus, when N ‐methylformamide (NMF) solutions of FeMoco either were titrated with measured aliquots of air or were diluted with air‐saturated NMF, [MoOS 3 ] 2− was found to be the predominant product while dilution of NMF solutions of FeMoco with air‐saturated methanol produced [MoS 4 ] 2− almost exclusively. Similar aerial oxidation of solutions of chemically synthesized Fe‐Mo‐S clusters showed that significant information about the molybdenum environment in these species could be deduced from the nature of the elicited thiomolybdates. The differences in decomposition products as a function of solvent are postulated to be due to the loss through precipitation of the reducing agent sodium dithionite on addition of methanol but not NMF. These overall decomposition results are discussed in the context of recent X‐ray absorption spectroscopic data which suggest the presence of an ‘MoS 3 ’ core in FeMoco. A possible mechanism wherby [MoS 4 ] 2− might be rapidly formed from this core is presented.