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evolution
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NifEN and MoFe protein have evolved from the replication and divergence of a common ancestral gene. NifEN is catalytically active early on in the course of evolution, when the mantle of earth is likely more reduced. Later, NifEN might have gradually evolved into an effective enzyme with a wide range of substrates, i.e. the MoFe protein, while in the meantime adjusting its own role toward synthesizing a catalytically more powerful cofactor, i.e. the iron-molybdenum cofactor
evolution
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substrate specificity and evolutionary implications of a recombinant chimeric NifDK enzyme carrying NifB-co at its active site, NifDK/NifB-co, overview
evolution
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the ability of V nitrogenase to catalyze both CO and N2 reductions suggests a potential link between the evolution of carbon and nitrogen cycles
evolution
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substrate specificity and evolutionary implications of a recombinant chimeric NifDK enzyme carrying NifB-co at its active site, NifDK/NifB-co, overview
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metabolism
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NifB and NifEN are two essential elements immediately adjacent to each other along the biosynthetic pathway of FeMoco. The 8Fe-precursor is present in the NifEN entity of a synthetic NifEN-B fusion protein, and additional [Fe4S4]-type cluster species are present in the NifB entity of NifEN-B. The cluster species in NifEN-B consist of both SAM-motif- and non-SAM-motif-bound [Fe4S4]-type clusters. The non-SAM-motif [Fe4S4]-cluster is a NifB-bound intermediate of FeMoco assembly, which could be converted to the 8Fe-precursor in a SAM-dependent mechanism
metabolism
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posttranslational regulation of nitrogenase activity in Rhodopseudomonas palustris depends on proteins DraT2, an ADP-ribosyltransferase, and GlnK2, an NtrC-regulated PII protein. GlnK2 is not well expressed in ammonium-grown NifA mutant cells that express nitrogenase genes constitutively and produce H2 when grown with ammonium as a nitrogen source. The mutant strain has elevated nitrogenase activity due to overexpression of the nif genes, and this increased amount of expression overwhelms a basal level of activity of DraT2 in ammonium-grown cells. Insufficient levels of both GlnK2 and DraT2 allow H2 production by an nifA* mutant grown with ammonium. Inactivation of the nitrogenase posttranslational modification system by mutation of draT2 results in increased H2 production by the ammonium-grown mutant cells
physiological function
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nitrogenase, an oxygen-labile enzyme typically containing an iron-molybdenum cofactor active site, is responsible for nitrogen fixation producing photobiological H2 as a byproduct
physiological function
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the conversion of N2 into NH3 is catalyzed by the nitrogenase enzyme, which is composed of two metalloproteins: NifDK, also termed dinitrogenase or MoFe protein, and NifH, also termed dinitrogenase reductase or Fe protein
physiological function
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the diminished H2 evolution by V nitrogenase originates from the diversion of electrons toward CO reduction, in contrast to the Mo nitrogenase
physiological function
the enzyme is involved in the N2 fixation mechanism, that proceeds via two different pathways, overview. N2 and NO2- reduction pathways converge upon reduction of NH2NH2 and NH2OH bound states to form state H with [-NH2] bound to the FeMo cofactor. Final reduction converts reaction intermediates H to I, with NH3 bound to the FeMo cofactor, supporting a N2 fixation mechanism in which liberation of the first NH3 occurs upon delivery of five [e-/H+] to N2, but a total of seven [e-/H+] to FeMo cofactor when obligate H2 evolution is considered, and not earlier in the reduction process
physiological function
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nitrogenase, an oxygen-labile enzyme typically containing an iron-molybdenum cofactor active site, is responsible for nitrogen fixation producing photobiological H2 as a byproduct
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physiological function
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the conversion of N2 into NH3 is catalyzed by the nitrogenase enzyme, which is composed of two metalloproteins: NifDK, also termed dinitrogenase or MoFe protein, and NifH, also termed dinitrogenase reductase or Fe protein
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additional information
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like the nif-encoded molybdenum nitrogenase, the vnf-encoded V nitrogenase is composed of a specific reductant and a catalytic component. Both nitrogenases use a catalytic mechanism that involves ATP-dependent electron transfer from a reductant, the nifH- or vnfH-encoded Fe protein, to the catalytic component, i.e. nifDK-encoded MoFe protein or vnfDGK-encoded VFe protein, and the reduction of N2 at the cofactor site, i.e. FeMoco or FeVco, of the latter
additional information
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NifEN plays an essential role in the biosynthesis of the nitrogenase iron-molybdenum, FeMo, cofactor. It is an alpha2beta2 tetramer that is homologous to the catalytic MoFe protein, NifDK, component of nitrogenase. NifEN serves as a scaffold for the conversion of an iron-only precursor to a matured form of the M cluster before delivering the latter to its target location within NifDK, NifEN crystal structure analysis, overview
additional information
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nitrogenase consists of the Fe protein, encoded by nifH, and the MoFe protein, encoded by nifD and nifK. The Fe protein is a homodimer containing a single [4Fe-4S] cluster and functions as an ATP-dependent electron donor to the MoFe protein, which is bound at the active site and alpha2beta2 heterotetramer with each nifD-encoded alpha subunit coordinating the FeMo cofactor that binds and reduces substrate, while alpha plus the nifK-encoded beta subunits coordinate the [8Fe-7S] P-cluster
additional information
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nitrogenase is a protein complex that is required for biological nitrogen fixation. It is made up of a nitrogenase, which is a NifD2/NifK2 heterotetramer, and a nitrogenase reductase, which is a homodimer of NifH
additional information
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pattern of nitrogenase activity during the light-dark cycle, overview
additional information
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pattern of nitrogenase activity during the light-dark cycle, overview
additional information
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primary sequences of NifEN and MoFe proteins
additional information
structure of the alpha70Ile MoFe protein compared to the alpha70Val wild-type MoFe protein, shows a delta-methyl group of alpha70Val that is positioned over Fe6 within the active site FeMo-cofactor
additional information
comparison of reaction mecanisms of nitrogenase, EC 1.18.6.1, and multiheme cytochrome c nitrite reductase, ccNIR, EC 1.7.2.2, overview
additional information
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nitrogenase consists of the Fe protein, encoded by nifH, and the MoFe protein, encoded by nifD and nifK. The Fe protein is a homodimer containing a single [4Fe-4S] cluster and functions as an ATP-dependent electron donor to the MoFe protein, which is bound at the active site and alpha2beta2 heterotetramer with each nifD-encoded alpha subunit coordinating the FeMo cofactor that binds and reduces substrate, while alpha plus the nifK-encoded beta subunits coordinate the [8Fe-7S] P-cluster
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additional information
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pattern of nitrogenase activity during the light-dark cycle, overview
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additional information
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pattern of nitrogenase activity during the light-dark cycle, overview
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