NNitrogenase, also called dinitrogenase, is the enzyme which catalyses the conversion of molecular nitrogen to ammonia (biological nitrogen fixation). The most widespread and most efficient nitrogenase contains a molybdenum cofactor. This entry, also known as the AnfK family, represents the beta subunit of the iron-only alternative nitrogenase []. It is homologous to NifK and VnfK, of the molybdenum-containing and the vanadium-containing nitrogenases, respectively.
Nitrogenase, also called dinitrogenase, is the enzyme which catalyses the conversion of molecular nitrogen to ammonia (biological nitrogen fixation) [, ]. The most widespread and most efficient nitrogenase contains a molybdenum cofactor. This protein family, VnfK, represents the beta subunit of the vanadium-containing V nitrogenase. It is homologous to NifK and AnfK, of the molybdenum-containing and the iron-only types, respectively.
Synonym: dark protochlorophyllide reductaseProtochlorophyllide reductase catalyzes the reductive formation of chlorophyllide from protochlorophyllide during biosynthesis of chlorophylls and bacteriochlorophylls. Three genes, bchL, bchN and bchB, are involved in light-independent protochlorophyllide reduction in bacteriochlorophyll biosynthesis. In cyanobacteria, algae, and gymnosperms, three similar genes, chlL, chlN and chlB are involved in protochlorophyllide reduction during chlorophylls biosynthesis. BchL/chlL, bchN/chlN and bchB/chlB exhibit significant sequence similarity to the nifH, nifD and nifK subunits of nitrogenase, respectively. Nitrogenase catalyzes the reductive formation of ammonia from dinitrogen []. The light-independent (dark) form of protochlorophyllide reductase plays a key role in the ability of gymnosperms, algae, and photosynthetic bacteria to form chlorophyll in the dark. Genetic and sequence analyses have indicated that dark protochlorophyllide reductase consists of three protein subunits that exhibit significant sequence similarity to the three subunits of nitrogenase, which catalyzes the reductive formation of ammonia from dinitrogen. Dark protochlorophyllide reductase activity was shown to be dependent on the presence of all three subunits, ATP, and the reductant dithionite.The BchL peptide (ChlL in chloroplast and cyanobacteria) is an ATP-binding iron-sulphur protein of the dark form protochlorophyllide reductase, an enzyme similar to nitrogenase [].
The enzyme responsible for nitrogen fixation, the nitrogenase, shows a high degree of conservation of structure, function, and amino acid sequence across wide phylogenetic ranges. All known Mo-nitrogenases consist of two components, component I (also called dinitrogenase, or Fe-Mo protein), an alpha2beta2 tetramer encoded by the nifD and nifK genes, and component II (dinitrogenase reductase, or Fe protein) a homodimer encoded by the nifH gene [, ]which has an Fe4S4 cluster bound between the subunits and two ATP-binding domains. The Fe protein supplies energy by ATP hydrolysis, and transfers electrons from reduced ferredoxin or flavodoxin to component 1 for the reduction of molecular nitrogen to ammonia [, ]. Nitrogenase contains two unusual rare metal clusters; one of them is the iron molybdenum cofactor (FeMo-co), which is considered to be the site of dinitrogen reduction and whose biosynthesis requires the products of the nifNE operon and of some other nif genes []. It has been proposed that nifNE might serve as a scaffold upon which FeMo-co is built and then inserted into component I [].This entry represents the nitrogenase iron protein (component II), which is encoded by nifH.
The enzyme responsible for nitrogen fixation, the nitrogenase, shows a high degree of conservation of structure, function, and amino acid sequence across wide phylogenetic ranges. All known Mo-nitrogenases consist of two components, component I (also called dinitrogenase, or Fe-Mo protein), an alpha2beta2 tetramer encoded by the nifD and nifK genes, and component II (dinitrogenase reductase, or Fe protein) a homodimer encoded by the nifH gene [, ]which has an Fe4S4 cluster bound between the subunits and two ATP-binding domains. The Fe protein supplies energy by ATP hydrolysis, and transfers electrons from reduced ferredoxin or flavodoxin to component 1 for the reduction of molecular nitrogen to ammonia [, ]. Nitrogenase contains two unusual rare metal clusters; one of them is the iron molybdenum cofactor (FeMo-co), which is considered to be the site of dinitrogen reduction and whose biosynthesis requires the products of the nifNE operon and of some other nif genes []. It has been proposed that nifNE might serve as a scaffold upon which FeMo-co is built and then inserted into component I [].This entry represents the uncharacterised N-terminal domain of the molybdenum-iron protein beta chain, which is part of the nitrogenase complex that catalyses the key enzymatic reactions in nitrogen fixation.
The enzyme responsible for nitrogen fixation, thenitrogenase, shows a high degree of conservation of structure, function, and amino acid sequence across wide phylogenetic ranges. All known Mo-nitrogenases consist of two components, component I (also called dinitrogenase, or Fe-Moprotein), an alpha2beta2 tetramer encoded by the nifD and nifK genes, and component II (dinitrogenase reductase, or Fe protein) a homodimer encoded by the nifH gene. Two operons, nifDK and nifEN, encode a tetrameric (alpha2beta2 and N2E2) enzymatic complex. Nitrogenase contains two unusual rare metal clusters; one of them is the iron molybdenum cofactor (FeMo-co), which is considered to be the site of dinitrogen reduction and whose biosynthesis requires the products of nifNE and ofsome other nif genes. It has been proposed that NifNE might serve as a scaffold uponwhich FeMo-co is built and then inserted into component I.This model represents the alpha chains of various forms of the nitrogen-fixing enzyme nitrogenase: vanadium-iron, iron-iron, and molybdenum-iron. Most examples of NifD, the molybdenum-iron type nitrogenase alpha chain, are excluded from this model and described instead by equivalog model .
The enzyme responsible for nitrogen fixation, the nitrogenase, shows a high degree of conservation of structure, function, and amino acid sequence across wide phylogenetic ranges. All known Mo-nitrogenases consist of two components, component I (also called dinitrogenase, or Fe-Mo protein), an alpha2beta2 tetramer encoded by the nifD and nifK genes, and component II (dinitrogenase reductase, or Fe protein) a homodimer encoded by the nifH gene [, ]which has an Fe4S4 cluster bound between the subunits and two ATP-binding domains. The Fe protein supplies energy by ATP hydrolysis, and transfers electrons from reduced ferredoxin or flavodoxin to component 1 for the reduction of molecular nitrogen to ammonia [, ]. Nitrogenase contains two unusual rare metal clusters; one of them is the iron molybdenum cofactor (FeMo-co), which is considered to be the site of dinitrogen reduction and whose biosynthesis requires the products of the nifNE operon and of some other nif genes []. It has been proposed that nifNE might serve as a scaffold upon which FeMo-co is built and then inserted into component I [].This entry refers to the alpha subunit of the MoFe protein (component I) of molybdenum (Mo-) nitrogenase, which is encoded by the nifD gene.
The enzyme responsible for nitrogen fixation, the nitrogenase, shows a high degree of conservation of structure, function, and amino acid sequence across wide phylogenetic ranges. All known Mo-nitrogenases consist of two components, component I (also called dinitrogenase, or Fe-Mo protein), an alpha2beta2 tetramer encoded by the nifD and nifK genes, and component II (dinitrogenase reductase, or Fe protein) a homodimer encoded by the nifH gene [, ]which has an Fe4S4 cluster bound between the subunits and two ATP-binding domains. The Fe protein supplies energy by ATP hydrolysis, and transfers electrons from reduced ferredoxin or flavodoxin to component 1 for the reduction of molecular nitrogen to ammonia [, ]. Nitrogenase contains two unusual rare metal clusters; one of them is the iron molybdenum cofactor (FeMo-co), which is considered to be the site of dinitrogen reduction and whose biosynthesis requires the products of the nifNE operon and of some other nif genes []. It has been proposed that nifNE might serve as a scaffold upon which FeMo-co is built and then inserted into component I [].This entry represents the molybdenum-iron protein beta chain, encoded by nifK.
The enzyme responsible for nitrogen fixation, the nitrogenase, shows a high degree of conservation of structure, function, and amino acid sequence across wide phylogenetic ranges. All known Mo-nitrogenases consist of two components, component I (also called dinitrogenase, or Fe-Mo protein), an alpha2beta2 tetramer encoded by the nifD and nifK genes, and component II (dinitrogenase reductase, or Fe protein) a homodimer encoded by the nifH gene [, ]which has an Fe4S4 cluster bound between the subunits and two ATP-binding domains. The Fe protein supplies energy by ATP hydrolysis, and transfers electrons from reduced ferredoxin or flavodoxin to component 1 for the reduction of molecular nitrogen to ammonia [, ]. Nitrogenase contains two unusual rare metal clusters; one of them is the iron molybdenum cofactor (FeMo-co), which is considered to be the site of dinitrogen reduction and whose biosynthesis requires the products of the nifNE operon and of some other nif genes []. It has been proposed that nifNE might serve as a scaffold upon which FeMo-co is built and then inserted into component I [].This entry refers to the nitrogenase MoFe cofactor biosynthesis protein encoded by the gene nifE.
The enzyme responsible for nitrogen fixation, the nitrogenase, shows a high degree of conservation of structure, function, and amino acid sequence across wide phylogenetic ranges. All known Mo-nitrogenases consist of two components, component I (also called dinitrogenase, or Fe-Mo protein), an alpha2beta2 tetramer encoded by the nifD and nifK genes, and component II (dinitrogenase reductase, or Fe protein) a homodimer encoded by the nifH gene [, ]which has an Fe4S4 cluster bound between the subunits and two ATP-binding domains. The Fe protein supplies energy by ATP hydrolysis, and transfers electrons from reduced ferredoxin or flavodoxin to component 1 for the reduction of molecular nitrogen to ammonia [, ]. Nitrogenase contains two unusual rare metal clusters; one of them is the iron molybdenum cofactor (FeMo-co), which is considered to be the site of dinitrogen reduction and whose biosynthesis requires the products of the nifNE operon and of some other nif genes []. It has been proposed that nifNE might serve as a scaffold upon which FeMo-co is built and then inserted into component I [].This entry refers to the nitrogenase iron-molybdenum cofactor biosynthesis protein NifN, which forms an alpha2beta2 tetramer with NifE. NifN and NifE are structurally homologous to nitrogenase MoFe protein beta and alpha subunits respectively [][]. NifB-co (an iron and sulfur containing precursor of the FeMoco) from NifB is transferred to the NifEN complex where it is further processed to FeMoco. The nifEN bound precursor of FeMoco has been identified as a molybdenum-free, iron- and sulfur- containing analog of FeMoco. It has been suggested that this nifEN bound precursor also acts as a cofactor precursor in nitrogenase systems which require a cofactor other than FeMoco: i.e. iron-vanadium cofactor (FeVco) or iron only cofactor (FeFeco) [].
