Another step towards engineering biological nitrogen fixation: diversity of NifB, the key to FeMo-co biosynthesis

Human population growth during the past 100 years has been supported by an almost unlimited supply of nitrogen-based fertilizers produced industrially through the Haber-Bosch process. Although this progress arguably brought the largest prosperity age in Human’s history, it has also generated severe environmental, economical and social costs. In particular, it has unbalanced the global nitrogen cycle to such an extent that it endangers Earth’s biosphere. Similarly to the Haber-Bosch cycle relying on metal catalyzers that transform N2 into NH3, the nitrogenase enzyme, responsible of the biological nitrogen fixation, needs a very complex iron-molybdenum cofactor (FeMoco) as its catalytic site. NifB is essential for building the FeMo-co metal structure. This work compiles the largest NifB database assembled to date and describe insights on NifB evolution, diversity, and structural-key elements. Importantly the work sketches a screening strategy to test the adequacy of NifB proteins for further implementation of FeMo-co (nitrogenase) biosynthesis in eukaryotes.