First active NifB protein purified from a eukaryotic cell

Development of N2 fixing cereal crops would revolutionize agricultural systems worldwide. In one approach to accomplish this goal, the genes encoding the prokaryotic enzyme nitrogenase must be transferred to the plant, and their encoded proteins must function in the eukaryotic environment. NifB is of utmost importance to this bioengineering process because it synthesizes a metal cluster (NifB-co) that is key to the biosyntheses of the active-site cofactors of all types of nitrogenases. In this work, synthetic versions of nifB from one bacterium and one archaeon were expressed in Saccharomyces cerevisiae and in Nicotiana benthamiana. The archaeon NifB was purified from aerobically grown yeast cells and found to be functional in nitrogenase cofactor biosynthesis, reaching a milestone in the process of engineering nitrogen fixing plants. This result highlights the importance of screening nif genes from different organisms in order to sort the best candidates to assemble a functional plant nitrogenase.