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QuickView for proteins iron- sulfur (biogroup)
- Description:
- 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).
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