Shared functions of Fe-S cluster assembly and Moco biosynthesis.

Molybdenum cofactor (Moco) biosynthesis is a complex process that involves the coordinated function of several proteins. In the recent years it has become evident that the availability of Fe-S clusters play an important role for the biosynthesis of Moco. First, the MoaA protein binds two [4Fe-4S] clusters per monomer.

Iron limitation indirectly reduces the operon expression by a reduction of molybdenum cofactor availability.

The expression of most molybdoenzymes in has so far been revealed to be regulated by anaerobiosis and requires the presence of iron, based on the necessity of the transcription factor FNR to bind one [4Fe-4S] cluster. One exception is trimethylamine--oxide reductase encoded by the operon, which has been described to be expressed independently from FNR. In contrast to other alternative anaerobic respiratory systems, the expression of the operon was shown not to be completely repressed by the presence of dioxygen.

A-Type Carrier Proteins Are Involved in [4Fe-4S] Cluster Insertion into the Radical -Adenosylmethionine Protein MoaA for the Synthesis of Active Molybdoenzymes.

Iron sulfur (Fe-S) clusters are important biological cofactors present in proteins with crucial biological functions, from photosynthesis to DNA repair, gene expression, and bioenergetic processes. For the insertion of Fe-S clusters into proteins, A-type carrier proteins have been identified. So far, three of them have been characterized in detail in Escherichia coli, namely, IscA, SufA, and ErpA, which were shown to partially replace each other in their roles in [4Fe-4S] cluster insertion into specific target proteins.