Nitrate Transport System in Neurospora crassa

摘要: Nitrate uptake in Neurospora crassa has been investigated under various conditions of nitrogen nutrition by measuring the rate disappearance nitrate from medium and determining mycelial accumulation. The transport system is induced either or nitrite, but not present mycelia grown on ammonia Casamino Acids. appearance activity prevented cycloheximide, puromycin, 6-methyl purine. displays a Km for 0.25 mM. inhibited metabolic poisons such as 2,4-dinitrophenol, cyanide, antimycin A. Furthermore, can concentrate 50-fold. Ammonia nitrite are non-competitive inhibitors with respect to nitrate, Ki values 0.13 0.17 mM, respectively. does repress formation system. In contrast, repressed All amino acids individually prevent accumulation, exception methionine, glutamine, alanine. influence reduction reductase protein was wild-type lacking functional non-utilizing mutants, nit-1, nit-2, nit-3. These contain an inducible which same characteristics those found having reductase. findings suggest that dependent upon these two processes separate events assimilation nitrate.