Mo-Fe Protein

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Nitrogen Fixation Nitrogen Fixation Part 1 Structure of Nitrogenase Components Fe Protein Mo-Fe Protein Mechanism of Nitrogenase Action Hydrogen Evolution Factors Affecting Nitrogenase Activity Nitrogen Fixation Genes Nitrification Nitrate Reduction Glutamate Synthase Pathway

Mo-Fe Protein

Mo-Fe Protein -
The Mo-Fe protein is a tetramer of MW 220,000245,000. It contains

(i) two molybdenum (Mo) atoms,
(ii) 28-34 nonhaeme iron (Fe) atoms, and
(iii) 26-28 labile sulphur atoms (S*). Fe and S* are present in about equal amounts.

This suggests that Fe is present in the typical iron sulphur cluster. The Mo Fe protein of c.pasteurianum, K. pneumoniae and A.vinelandii is composed of two copies each of two dissimilar subunits (α2β2).

The subunits have MW of about 50,000 and 60,000. The two subunits are distinct proteins rather than alterations of one protein.

Similarities between the subunits are probably the result of gene duplication that may have occurred during the evolution of nitrogenase.

One subunit is coded by the nifD gene and the other by the nifD gene. Each subunit requires the other for stability in vivo. When a mutation in either gene makes its product unstable, the other gene product is also rapidly degraded.

The Mo-Fe protein of the bacterial species mentioned above is complexed with:
(i) Up to 4 Fe₄S^*₄ centers (16 Fe atoms),

(ii) Two centres that appear to contain MoFe₆S^*6 called the FeMo cofactor or FeMo-co (12 Fe atoms), and

(iii) Possibly also a Fe₂S₂center (2Fe atoms).

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Nitrogen Fixation Part 1 Ammonification Denitrification Denitrifying Bacteria Ecological Importance of Denitrification Nitrogen Assimilation Transamination Glutamate Dehydrogenase (GDH) Glutamate Synthase Pathway Glutamine Synthetase (GS) Reaction Glutamate Synthase (GOGAT) Reaction Transaminase Reactions Glutamine Synthtase Adenylylation and Deadenylylation

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