Nitrogenase third component

Fe component property Mo nitrogenase V nitrogenase Third nitrogenase... 

A preparation of the third nitrogenase from A. vinelandii, isolated from a molybdenum-tolerant strain but lacking the structural genes for the molybdenum and vanadium nitrogenases, was discovered to contain FeMoco 194). The 8 subunit encoded by anfG was identified in this preparation, which contained 24 Fe atoms and 1 Mo atom per mol. EPR spectroscopy and extraction of the cofactor identified it as FeMoco. The hybrid enzyme could reduce N2 to ammonia and reduced acetylene to ethylene and ethane. The rate of formation of ethane was nonlinear and the ethane ethylene ratio was strongly dependent on the ratio of nitrogenase components. 

The components of the third nitrogenase, analogous to the MoFe and VFe proteins (dinitrogenase-3) have been purified and partially characterized (5). The third nitrogenase can be isolated in two active forms with different subunit configurations, ai/ 2 and a2(32 there is a 8 subunit present at uncertain stoichiometry encoded by anfG (R. Eady and R. Pau, unpublished). 

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