Nitrogenase FeFe protein

Iron nitrogenase. FeFe proteins (e.g. from Azotobacter vinelandii and Rhodopseudomonas capsulatus) are hexameric (02 2 2) actually contain low... 

An Fe-only nitrogenase has also been isolated from a nifH mutant of Rhodospirillum rubrum and was characterized as an a2/82<% hex-amer containing only iron, no molybdenum or vanadium, with an o 2Fe4S4-containing Fe protein. A factor could be extracted from the FeFe protein into NMF that combined with apo-MoFe protein to form an active enzyme 193). 

Gollan, U., Schneider, K., Muller, A., Schuddekopf, K., and Klipp, W. 1993. Detection of the in vivo incorporation of a metal cluster into a protein. The FeMo cofactor is inserted into the FeFe protein of the alternative nitrogenase in Rhodobacter capsulatus. Eur. J. Biochem. 215, 25-35. 

The iron-only nitrogenase has been isolated from A. vinelandii, R. rubum, and R. capsulatus (Table 1). It is also similar to the molybdenum nitrogenase except that the molybdenum is replaced by iron in the protein. It has the molybdenum iron (MoFe) protein equivalent in the iron-iron (FeFe) protein and the iron (Fe) protein equivalent. 

A second iron metalloprotein that is larger (about 220.000 Daltons) and also eventually contains another transition metal that is different for the three kinds of nitrogenase enzymes Mo (MoFe protein), V (VFe protein) or Fe (FeFe protein). It is the MoFe protein that is tiie best known. It contains ... 

For the most common types of biological clusters ([2Fe-2S], [3Fe-4S], and [4Fe-4S]), the assembly machinery includes iron chaperones, cysteine desulfurases, electron transfer proteins, molecular chaperones, and scaffold proteins on which the nascent cluster is assembled prior to insertion into a target protein. For the more complex and unusual clusters, such as FeMoco of nitrogenase, the [NiFe] center of hydrogenase, or the Fl-cluster of [FeFe] hydrogenase, significantly less is known about the cluster assembly process. As we shall discover below, one common theme that these systems share in the synthesis of their respective metallocofactors is the involvement of radical chemistry provided by radical SAM enzymes. 

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