Nitrogenase is a complex metalloenzyme that catalyzes one of the most remarkable chemical transformations in biological systems: the nucleotide-dependent reduction of atmospheric dinitrogen to bioavailable ammonia. There is an outstanding interest in decoding the assembly mechanism of nitrogenase, not only because of its significant relevance to nitrogenase-specific reactions, but also because of its tremendous implication for general metalloprotein biogenesis. Here we propose to greatly expand our understanding of the nitrogenase assembly process by combined genetic, biochemical, spectroscopic and structural approaches. The MoFe protein of the molybdenum nitrogenase of Azotobacter vinelandii will be the focus of the proposed investigation. Through our proposed studies, we expect to further refine the biosynthetic pathways of MoFe protein and its associated clusters, a continuous effort with an ultimate goal to unravel the molecular mechanism of nitrogenase assembly. Furthermore, using nitrogenase as a model system, we also hope to provide general themes of biological metal cluster assembly, which may, in the long run, prove instrumental in developing successful strategies for the chemical synthesis of complex metalloclusters. .

Public Health Relevance

Nitrogenase catalyzes the transformation of atmospheric dinitrogen to bioavailable ammonia, thereby supplying the reduced nitrogen, an essential component of nucleic acids and proteins, for the existence of human population. This particular proposal deals with the assembly of nitrogenase MoFe protein and its associated metalloclusters and the outcome of these studies will hopefully provide general themes of biological metal cluster assembly and facilitate future development of cost-efficient strategies for the chemical synthesis of catalytically active metalloclusters. As such, our proposed research may have additional economic value in addition to its intrinsic relevancy to human health.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Macromolecular Structure and Function A Study Section (MSFA)
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Fabian, Miles
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University of California Irvine
Schools of Arts and Sciences
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Lee, Chi Chung; Sickerman, Nathaniel S; Hu, Yilin et al. (2016) YedY: A Mononuclear Molybdenum Enzyme with a Redox-Active Ligand? Chembiochem 17:453-5
Hu, Yilin; Ribbe, Markus W (2016) Maturation of nitrogenase cofactor-the role of a class E radical SAM methyltransferase NifB. Curr Opin Chem Biol 31:188-94
Fay, Aaron W; Blank, Michael A; Rebelein, Johannes G et al. (2016) Assembly scaffold NifEN: A structural and functional homolog of the nitrogenase catalytic component. Proc Natl Acad Sci U S A 113:9504-8
Cahn, Jackson K B; Brinkmann-Chen, Sabine; Spatzal, Thomas et al. (2015) Cofactor specificity motifs and the induced fit mechanism in class I ketol-acid reductoisomerases. Biochem J 468:475-84
Wiig, Jared A; Hu, Yilin; Ribbe, Markus W (2015) Refining the pathway of carbide insertion into the nitrogenase M-cluster. Nat Commun 6:8034
Lee, Chi Chung; Fay, Aaron W; Weng, Tsu-Chien et al. (2015) Uncoupling binding of substrate CO from turnover by vanadium nitrogenase. Proc Natl Acad Sci U S A 112:13845-9
Lee, Chi Chung; Hu, Yilin; Ribbe, Markus W (2015) Catalytic reduction of CN-, CO, and CO2 by nitrogenase cofactors in lanthanide-driven reactions. Angew Chem Int Ed Engl 54:1219-22
Tanifuji, Kazuki; Lee, Chi Chung; Ohki, Yasuhiro et al. (2015) Combining a Nitrogenase Scaffold and a Synthetic Compound into an Artificial Enzyme. Angew Chem Int Ed Engl 54:14022-5
Lee, Chi Chung; Hu, Yilin; Ribbe, Markus W (2015) Insights into hydrocarbon formation by nitrogenase cofactor homologs. MBio 6:
Ribbe, Markus W (2015) Insights into the Mechanism of Carbon Monoxide Dehydrogenase at Atomic Resolution. Angew Chem Int Ed Engl 54:8337-9

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