Azobacter vinelandii

A cofactor can be extracted from the iron-molybdenum protein, using Af-methylformamide. This cofactor (called FeMoCo) has many spectroscopic properties in common with the native protein, especially the EXAFS spectrum, and activates the inactive large protein derived from Azobacter vinelandii UW45 mutant which cannot incorporate molybdenum. The cofactor contains no protein or peptide, but does contain molybdenum, iron, and sulfur in atomic ratios of 1 6-8 4-9. It is believed to contain the dinitrogen-binding site (presumably molybdenum) but there is no definitive proof of this. 

JDFT] J. L. Jost, J. F. Drake, A. G. Fredrickson, and H. M. Tsuchiya (1973), Interaction of Tetrahymena pyriformis, Escherichia coli, Azobacter vinelandii and glucose in a minimal medium, Journal of Bacteriology 113 834-40. 

C-methyl-4-(methylamino)-L-mannose (sibirosamine), both similar to callipeltose, were found to be part of nucleosides isolated from cultures of Azobacter vinelandii [135] and as the saccharide moiety of sibiromycin, an antitumor antibiotic isolated from Streptosporangium sibiricum [136]. 

Aspartate a [112] Rhizobium trifoU Rhizobium leguminosarum E. coli Azobacter vinelandii Aspartate /S-Alanine... 

Thiol extrusion of the FeS centres from Azobacter vinelandii and Clostridium pasteurianum with alkyl fluorothiols allows identification of at least two Fe4S4 and one FegSj cluster in the (Fe-Mo) protein. A cluster model in which two Fe4S4 units are bridged through a comer iron on each cube by a Mo S4 unit is proposed for the active site of the (Fe-Mo) cofactor. Molecular nitrogen binds axially to the central molybdenum and is Ji-bonded to the iron in the cubes. This weakens and activates the N=N bond and electrons are injected stepwise via the two iron-sulphur cubes with successive protonation at the terminal N. This latter point is consistent with a report that N—NHg is important in nitrogen fixation. 

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