Regulation of nitrogen fixation. Nitrogenase-derepressed mutants of Klebsiella pneumoniae.
1. A new procedure is described for selecting nitrogenase-derepressed mutants based on the method of Brenchley et al. (Brenchley, J.E., Prival, M.J. and Magasanik, B. (1973) J. Biol. Chem. 248, 6122-6128) for isolating histidase-constitutive mutants of a non-N2-fixing bacterium. 2. Nitrogenase levels of the new mutants in the presence of NH4+ were as high as 100% of the nitrogenase activity detected in the absence of NH4+. 3. Biochemical characterization of these nitrogen fixation (nif) derepressed mutants reveals that they fall into three classes. Three mutants (strains SK-24, 28 and 29), requiring glutamate for growth, synthesize nitrogenase and glutamine synthetase constitutively (in the presence of NH4+). A second class of mutants (strains SK-27 and 37) requiring glutamine for growth produces derepressed levels of nitrogenase activity and synthesized catalytically inactive glutamine synthetase protein, as determined immunologically. A third class of glutamine-requiring, nitrogenase-derepressed mutants (strain SK-25 and 26) synthesizes neither a catalytically active glutamine synthetase enzyme nor an immunologically cross-reactive glutamine synthetase protein. 4. F-prime complementation analysis reveals that the mutant strains SK-25, 26, 27, 37 map in a segment of the Klebsiella chromosome corresponding to the region coding for glutamine synthetase. Since the mutant strains SK-27 and SK-37 produce inactive glutamine synthetase protein, it is concluded that these mutations map within the glutamine synthetase structural gene.
D000641:Ammonia / Q000494:pharmacology; D002874:Chromosome Mapping; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000276:immunology / Q000378:metabolism; D006824:Hybridization, Genetic; D005779:Immunodiffusion; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000378:metabolism*; D009154:Mutation; D009586:Nitrogen Fixation / Q000187:drug effects; D009591:Nitrogenase / Q000378:metabolism*; D010641:Phenotype; D013045:Species Specificity
D000641:Ammonia; D009591:Nitrogenase; D005969:Glutamate Dehydrogenase; D005974:Glutamate-Ammonia Ligase