A new theory suggests that nitrogenase from cyanobacteria could be the reason oxygen levels remained low after the Great Oxidation Event.

Abstract. Generating crops that utilize atmospheric nitrogen rather than soil nitrogen requires the transfer of nitrogenase structural genes together with

What happens when D2 enters the nitrogenase gallery of H atom donors?

Abstract. Generating crops that utilize atmospheric nitrogen rather than soil nitrogen requires the transfer of nitrogenase structural genes together with

Abstract. Crop productivity relies on synthetic nitrogen fertilizers, which entail significant economic and environmental costs. Engineering crop plants to

Gram-positive and facultatively anaerobic Paenibacillus polymyxa is a model diazotroph whose nif (nitrogen fixation) genes encoding nitrogenase have been used for engineering yeast and plants. However, the pathway of electron transfer to Paenibacillus nitrogenase is unknown. In this study, we demonstrate that Fd encoded by cbiW and PFOR encoded by the pfoAB operon constitute an electron transport pathway to Paenibacillus nitrogenase. Fd encoded by cbiW is a [2Fe-2S] Fd, and PFOR encoded by the…

Many photosynthetic bacteria rely on the nitrogenase-like dark-operative protochlorophyllide oxidoreductase (DPOR) to sustain (bacterio)chlorophyll synthesis in the dark. DPOR couples ATP hydrolysis to electron transfer from a reducing component (L-protein) to a catalytic component (NB-protein) that reduces protochlorophyllide. NB-protein is an α2β2 heterotetramer, and each heterodimeric half contains an active site and a [Fe4S4] cluster. Although the two halves are identical, they react sequen…

Symbiotic nitrogen fixation (SNF) by legumes and rhizobia is a highly energy demanding mode of biological nitrogen fixation. Although the nitrogenase reaction defines the theoretical minimum energy requirement, how energy is supplied, consumed, and regulated across symbiotic stages remains incompletely understood. In this review, we use energy economics as an interpretive framework to examine how legumes and rhizobia coordinate energy supply and demand, how multilevel regulatory networks shape carbon–nitrogen exchange and nitrogen conversion efficiency, and how energy sourcing and allocation vary across symbiotic stages, organs, nodule zones, and cell types. Furthermore, we briefly consider whether lipid derived metabolites contribute to nodule carbon metabolism under specific conditions, noting that direct evidence that lipid derived carbon enters bacteroid central metabolism, fuels respiration, or supports nitrogenase activity remains lacking. We also discuss stress induced reprogramming of symbiotic energy allocation in horticultural legumes. We further highlight the limitations of bulk omics and the potential of high resolution spatiotemporal multi omics to resolve metabolic heterogeneity among nodule zones and cell types. Finally, we propose a framework for systematic research encompassing “spatiotemporal atlas resolution—validation of coupling driving forces—predictive model construction”. In summary, this review conceptualizes energy intensive SNF as a multilevel supply demand system and shifts the analysis of SNF from macroscopic description to identifiable, quantitative, and predictable control nodes. This perspective provides a fresh analytical basis for optimizing energy allocation strategies during SNF and lays a theoretical foundation for designing low energy, high efficiency symbiotic systems through synthetic biology.

Nitrogenase requires low-potential electrons to reduce N2 to produce ammonia. The direct electron donors to nitrogenase are reduced ferredoxin (Fd) and flavodoxin (Fld). The enzymes that reduce Fd or Fld for N2 fixation mainly include pyruvate-flavodoxin (ferredoxin) oxidoreductase (PFOR), ferredoxin-NADP+ reductase (FNR), Rhodobacter nitrogen fixation protein complex (Rnf), and bifurcating electron transfer flavoprotein complex (Fix). Paenibacillus polymyxa is a model for studies of nitrogen fixation, but the pathways of electron transport to nitrogenase are unknown. In this study, we characterized the electron transport pathway to nitrogenase in P. polymyxa. Deletion analysis showed that among 15 genes encoding Fds, Fld, and Fd-/Fld-reducing enzymes, only cbiW gene and pfoAB operon decreased nitrogenase activity (31% and 37% relative to wild type, respectively). Triple deletion of cbiW and pfoAB led to a reduction of nitrogenase activity by 61%. Elemental analysis and ultraviolet-visible absorption spectroscopy revealed that the purified Fd protein encoded by cbiW is a [2Fe-2S] Fd. The purified Fd protein was able to substitute for Klebsiella NifF (Fld) to transfer electrons from pyruvate to Klebsiella nitrogenase in vitro. The pfoAB operon encodes PFOR, which is composed of two subunits. Klebsiella oxytoca NifJ (PFOR) was able to support nitrogen fixation in the ΔpfoAB mutant. These findings suggest that [2Fe-2S] Fd encoded by cbiW and PFOR encoded by the pfoAB operon constitute an electron transport pathway to Paenibacillus nitrogenase.

Generating crops that utilize atmospheric nitrogen rather than soil nitrogen requires the transfer of nitrogenase structural genes together with genes required for the biosynthesis of nitrogenase iron−sulfur cofactors. Scaffold proteins, such as NifU, are the starting point of nitrogenase cofactor assembly. While NifU has been successfully produced in plants, its optimal production was achieved with iron supplementation in the nutrient solution. This suggests a faulty connection with the endogenous iron trafficking network, indicating the need for specific elements targeting iron to NifU. Here, we identify bacterioferritin A (BfrA) as an iron donor to NifU. Co-expression with BfrA increases NifU production in Nicotiana benthamiana, leading to doubling the production of NifH, a nitrogenase structural protein that is also required for the synthesis of more complex nitrogenase cofactors. This work underscores the importance of transferring metal delivery systems alongside metalloproteins when engineering heterologous systems.

Proceedings of the National Academy of Sciences, Volume 123, Issue 43, October 2026. SignificanceMethane acts as a potent greenhouse gas and its release into the atmosphere significantly contributes to global warming, raising substantial interest in understanding the basic processes underlying biological methane formation. The CfbC/D ...

Nitrogenase catalyzes the ATP-dependent reduction of dinitrogen to ammonia, a key step in the global nitrogen cycle. The Mo- and V-dependent nitrogenase isozymes are expressed under different environmental conditions, including temperature, yet little is known about how their catalytic behavior changes with temperature. Here, we examine the temperature dependence of total electron flux, electron partitioning into the products NH3 and H2, and estimate ATP energy costs per N2 fixed for purified Mo- and V-nitrogenases from Azotobacter vinelandii over a 10-50 ˚C temperature range. Both isozymes exhibit similar temperature-dependent scaling of total electron flux to all products across the temperature range, but with significantly different distributions of electrons to H2 or NH3 formation. As temperature increases, V-nitrogenase diverts an increasing fraction of electron flux into H2 formation, whereas Mo-nitrogenase maintains a nearly constant electron partitioning to N2 reduction. The estimated ATP molecules hydrolyzed per N2 reduced change little for the Mo-nitrogenase across this temperature range, but rises significantly for the V-nitrogenase with increasing temperature, reaching over 200 ATP per N2 fixed at 50 ˚C. These results demonstrate that, in A. vinelandii, the Mo- and V-nitrogenases exhibit significantly different responses of electron partitioning to products and ATP hydrolyzed per N2 reduced to changes in temperature. These findings suggest environmental conditions under which each isozyme would be optimal, with V- and Mo-nitrogenase both being favorable at low temperatures and Mo-nitrogenase being the only energetically reasonable enzyme at higher temperatures.

Equipes da Saint Louis University e da University of Arkansas usaram microscopia crioeletrônica em condições sem oxigênio para revelar uma estrutura desconhecida da nitrogenase. O achado, publicado na Nature, contradiz suposições de décadas e pode inspirar biotecnologias para uma agricultura menos poluente.

Abstract. Molybdenum nitrogenase catalyzes biological nitrogen fixation using a complex metallocofactor (FeMoco) containing three μ2-“belt”sulfides that ex

Quantum algorithms face a new benchmark as classical methods achieve chemical accuracy—1 kcal/mol—in modeling the FeMo cofactor of nitrogenase.

Cryo-electron microscopy of a nitrogenase supercomplex from a methane-producing archaeon reveals a mechanism in which PII proteins drive assembly of such structures to regulate nitrogenase activity in response to nitrogen availability.