• Applied Biological Chemistry
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• v.48 no.3
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• pp.189-200
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• 2005

Biological nitrogen fixation is an important process for academic and industrial aspects. This review will briefly compare industrial and biological nitrogen fixation and cover the characteristics of biological nitrogen fixation studied in Azotobacter vinelandii. Various organisms can carry out biological nitrogen fixation and recently the researches on the reaction mechanism were concentrated on the free-living microorganism, A. vinelandii. Nitrogen fixation, which transforms atmospheric $N_2$ into ammonia, is chemically a reduction reaction requiring electron donation. Nitrogenase, the biological nitrgen fixer, accepts electrons from biological electron donors, and transfers them to the active site, FeMo-cofactor, through $Fe_4S_4$ cluster in Fe protein and P-cluster in MoFe protein. The electron transport and the proton transport are very important processes in the nitrogenase catalysis to understand its reaction mechanism, and the interactions between FeMo-cofactor and nitrogen molecule are at the center of biological nitrogen fixation mechanism. Spectroscopic studies including protein X-ray crystallography, EPR and $M{\ddot{o}}ssbauer$, biochemical approaches including substrate and inhibitor interactions as well as site-directed mutation study, and chemical approach to synthesize the FeMo-cofactor model compounds were used for biological nitrogen fixation study. Recent research results from these area were presented, and finally, a new nitrogenase reaction mechanism will be proposed based on the various research results.

• Molecules and Cells
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• v.46 no.12
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• pp.736-742
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• 2023

NifB, a radical S-adenosylmethionine (SAM) enzyme, is pivotal in the biosynthesis of the iron-molybdenum cofactor (FeMo-co), commonly referred to as the M-cluster. This cofactor, located within the active site of nitrogenase, is essential for the conversion of dinitrogen (N₂) to NH₃. Recognized as the most intricate metallocluster in nature, FeMo-co biosynthesis involves multiple proteins and a sequence of steps. Of particular significance, NifB directs the fusion of two [Fe₄S₄] clusters to assemble the 8Fe core, while also incorporating an interstitial carbide. Although NifB has been extensively studied, its molecular mechanisms remain elusive. In this review, we explore recent structural analyses of NifB and provide a comprehensive overview of the established catalytic mechanisms. We propose prospective directions for future research, emphasizing the relevance to biochemistry, agriculture, and environmental science. The goal of this review is to lay a solid foundation for future endeavors aimed at elucidating the atomic details of FeMo-co biosynthesis.

• Proceedings of the Korea Crystallographic Association Conference
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• 2005.11a
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• pp.8-9
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• 2005

• Bulletin of the Korean Chemical Society
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• v.27 no.1
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• pp.35-36
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• 2006

• Proceedings of the Korean Biophysical Society Conference
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• 2002.06b
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• pp.18-18
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• 2002

Nitrogenase, comprised of the MoFe and Fe proteins, catalyzes the reduction of dinitrogen to ammonia at ambient temperature and pressure. The MoFe protein contains two metal centers, the P-cluster (Fe8S7-8) and the FeMo-cofactor (Fe7S9：homocitrate), the substrate binding site. Despite the availability of the crystal structure of the MoFe protein, suprisingly little is known about the molecular details of catalysis at the active site, and no small-molecule substrate or inhibitor had ever been shown to directly interact with a protein-bound cluster of the functioning enzyme, until our electron-nuclear double resonance(ENDOR) study of CO-inhibited nitrogenase.(omitted)