FeMo, synthesis

Synthesis of metal-organic cofactors Molybdopterin-cofactor in dehydrogenases FeMo-cofactor for nitrogenase... 

A) clusters. To date, it has not proven possible to isolate a cluster in which only one of the trigonal faces is capped by an Mo(C0)3 fragment, although such species are in equilibrium with the dicapped cluster in solution (7A). This system represents one of the very few Mo-Fe-S clusters in which the detailed structure of the product was anticipated prior to its synthesis. If the problems associated with forming a monocapped species and subsequent oxidative decarbonylation at Mo can be overcome, these complexes will Indeed be the closest synthetic representations to FeMo-co yet achieved. 

X, N, Ep and H are needed for synthesis of FeMo-co and for its incorporation into the MoFe-protein.55/55a Nif A is an activator gene for the whole duster including the nifL gene product, which is altered by the presence of 02 or of glutamine. Accumulation of the latter in cells (see Section B,2) strongly represses transcription of the nitrogenase genes. 

The future synthetic models of FeMo-co will have to closely resemble the now more accurate MoFc7S9Y crystallographic model (with Y probably being N). The progress made in the synthesis of P-cluster analogues, discussed in the previous... 

In addition to the mechanistic role in the nitrogenase enzymatic function, Fe-protein also participates at several stages in the biosynthesis of the nitrogenase proteins. Fe-protein is essential for the production of active MoFe-protein and is involved in both the synthesis of FeMo-cofactor and its insertion into cofactor-deficient MoFe-protein (40-42). Fe-protein may also function as an activator for the expression of alternative nitrogenases (43). In turn, formation of active Fe-protein requires the nifM gene product (44, 45), which perhaps functions either in cluster insertion or in promoting the correct subunit-subunit and subunit-cofactor interactions in the Fe-protein dimer (i.e., a chaperone-type role). The significant sequence conservation observed in the Fe-protein family may reflect the structural constraints associated with these diverse aspects of Fe-protein function. 

The reaction of ME4" with iron salts has resulted in the formation of a number of heterometallic M/Fe clusters. Several of these complexes exhibit structural relationships to the FeMo-cofactor and P-cluster of the enzyme nitrogenase, with research directed towards the synthesis of... 

---