title: In vitro restoration of nitrate reductase: investigation of Aspergillus nidulans and Neurospora crassa nitrate reductase mutants.
abstract: Extracts of Aspergillus nidulans wild type (bi-1) and the nitrate reductase mutant niaD-17 were active in the in vitro restoration of NADPH-dependent nitrate reductase when mixed with extracts of Neurospora crassa, nit-1. Among the A. nidulans cnx nitrate reductase mutants tested, only the molybdenum repair mutant, cnxE-14 grown in the presence of 10-minus 3 M Na2 MoO4 was active in the restoration assay. Aspergillus extracts contained an inhibitor(s) which was measured by the decrease in NADPH-dependent nitrate reductase formed when extracts of Rhodospirillum rubrum and N. crassa, nit-1 were incubated at room temperature. The inhibition by extracts of A. nidulans, bi-1, cnxE-14, cnxG-4 and cnxH-3 was a linear function of time and a logarithmic function of the protein concentration in the extract. The molybdenum content of N. crassa wild type and nit-1 mycelia were found to be similar, containing approx. 10 mu g molybdenum/mg dry mycelium. The NADPH-dependent cytochrome c reductase associated with nitrate reductase was purified from both strains. The NADPH-dependent cytochrome c reductase associated with nitrate reductase was purified from both strains. The enzyme purified from wild-type N. crassa contained more than 1 mol of molybdenum per mol of enzyme, whereas the enzyme purified from nit-1 contained negligible amounts of molybdenum.
mesh_terms: D001233:Aspergillus nidulans / Q000201:enzymology; D003579:Cytochrome Reductases / Q000032:analysis; D008982:Molybdenum / Q000032:analysis / Q000378:metabolism*; D009154:Mutation; D009491:Neurospora / Q000201:enzymology*; D009492:Neurospora crassa / Q000032:analysis / Q000201:enzymology*; D009565:Nitrate Reductases / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010936:Plant Extracts / Q000494:pharmacology; D014176:Protein Biosynthesis; D013045:Species Specificity
chemical_list: D010936:Plant Extracts; D008982:Molybdenum; D003579:Cytochrome Reductases; D009565:Nitrate Reductases