Unlocking a Simpler Path to Nitrogen Fixation

What is it about?

Nitrogenase is an enzyme composed of the NifH and NifDK proteins that reduces dinitrogen to ammonia. The nitrogenase active site embedded in NifDK contains an iron-molybdenum cofactor (FeMo-co), which is synthesized externally on the NifEN protein, a homolog of NifDK. In our study, we have identified the first nitrogenase in nature, discovered in a thermophilic bacterium, that can mature its own FeMo-co independently of NifEN. This finding challenges the long-standing paradigm that a minimum set of nifHDKBEN genes is necessary for the assembly of a functional molybdenum nitrogenase. Remarkably, this new nitrogenase exhibits a dual role —it serves both as a catalyst for dinitrogen reduction and as a self-sufficient maturase for its cofactor. This finding represents a groundbreaking in the understanding of nitrogenase biosynthesis and evolution.

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Photo by National Institute of Allergy and Infectious Diseases on Unsplash

Photo by National Institute of Allergy and Infectious Diseases on Unsplash

Why is it important?

This unique nitrogenase may resemble an ancestral enzyme that combined catalytic and maturase activities, potentially simplifying the pathway for FeMo-co synthesis prior to the divergence of NifDK and NifEN. This discovery is not only a major step in understanding the evolution of nitrogenases but also has transformative potential for nitrogenase engineering. It could simplify the engineering of functional nitrogenase into eukaryotic cells, paving the way for crops capable of utilizing atmospheric N₂. Such innovation would mark a significant leap toward sustainable agriculture by reducing dependence on industrial fertilizers.

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