A dynamic tool for nitrogen reduction

Even though nitrogen makes up almost 80% of the atmosphere, it is a limiting nutrient for biomass production. The low reactivity of nitrogen gas (N2) is a result of its very strong, unpolarized triple bond. Nitrogenase is the only enzyme known that can break this bond to produce compounds such as ammonia (NH3) for use in biosynthetic pathways. The atomic structure of this amazing system has been known for more than two decades (1, 2), but the chemical mechanism of this central reaction remains unknown. In a biochemical and structural tour de force, on page 1620 of this issue, Spatzal et al. (3) report the crystal structure of carbon monoxide (CO) bound to the catalytic metal cluster of the enzyme. This work revealed an unexpected structural rearrangement of the cofactor