Biological nitrogen fixation is restricted to a subset of microbes that have the capacity to express active nitrogenase and therefore reduce nitrogen gas into ammonia. The enzyme reactivity relies on the coordination of the metalloclusters mediating electron transfer events and substrate binding and reduction. Thus, besides the expression of catalytic units, a consortium of additional components is required for the assembly, trafficking, and insertion of metalloclusters critical of the enzyme’s functionality. The aerobe diazotroph <i>Azotobacter vinelandii</i> encodes the three known types of nitrogenase, Mo-, V- and Iron-dependent enzymes; and each becomes functional under distinct metal availability conditions. The synthesis of metalloclusters destined to these enzymes involves dedicated pathways initiated by assembling simple units of [Fe-S] clusters in reactions catalyzed by cysteine desulfurases and cluster scaffold. In this work, we have employed a combination of genetic and biochemical approaches to investigate the involvement of NifU along with AnfU and VnfU for the synthesis and transfer of initial Fe-S cluster units destined to alternative nitrogenases.

Synthesis and trafficking of initial Fe-S units destined to nitrogenases

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