title: Nitrogen fixation by Azotobacter vinelandii in tungsten-containing medium.
abstract: Nitrogenase was isolated and purified from wild-type and a tungsten-resistant mutant (LM2) of Azotobacter vinelandii strain OP derepressed on medium containing 1-10 mM W. While the enzyme from the wild-type strain contained the polypeptides of the conventional enzyme, metal analysis of component 1 demonstrated the existence of one atom each of molybdenum and tungsten. Furthermore, the ESR spectrum of this protein contained three signals, two of which originated from S = 3/2 spin states. One of these signals is nearly identical to that of the conventional MoFe-protein while the other is hypothesized to originate from a W-containing cofactor. In spite of the presence of W, the substrate reduction pattern of this enzyme is the same as that of the conventional enzyme.
mesh_terms: D001395:Azotobacter / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D009154:Mutation; D009586:Nitrogen Fixation / Q000187:drug effects*; D009591:Nitrogenase / Q000378:metabolism*; D014414:Tungsten / Q000494:pharmacology*
chemical_list: D009591:Nitrogenase; D014414:Tungsten