The product of the Klebsiella pneumoniae nifX gene is a negative regulator of the nitrogen fixation (nif) regulon

• Published in: Journal of Bacteriology 1990-03, Vol.172 (3), p.1441-1447
• Main Authors: Gosink, M.M. (University of Wisconsin-Madison, Madison, WI), Franklin, N.M, Roberts, G.P
• Format: Article
• Language: English
• Subjects: Acetylene - metabolism; ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; Bacterial Proteins - biosynthesis; Bacterial Proteins - isolation & purification; Blotting, Northern; Blotting, Southern; COMPOSE DE L'AMMONIUM; COMPUESTOS DE AMONIO; DNA Transposable Elements; Electrophoresis, Gel, Two-Dimensional; FIJACION DEL NITROGENO; FIXATION DE L'AZOTE; GENE; GENES; Genes, Bacterial; Genes, Regulator; Kinetics; KLEBSIELLA; Klebsiella pneumoniae - genetics; Klebsiella pneumoniae - metabolism; Mutation; Nitrogen Fixation - genetics; NITROGENASA; NITROGENASE; OXIGENO; OXYGENE; Plasmids; Regulatory Sequences, Nucleic Acid; Restriction Mapping
• ISSN: 0021-9193; 1098-5530; 1067-8832
• DOI: 10.1128/jb.172.3.1441-1447.1990

An insertional mutation was made in the nifX gene of Klebsiella pneumoniae. This mutation had little effect on the nitrogenase activity of the strain, as measured by acetylene reduction. However, on the addition of NH4+ or O2 (conditions which block nif protein synthesis by transcriptional and posttranscriptional mechanisms), the NifX- mutant synthesized nitrogenase proteins longer and had more accumulated nifHDKTY mRNA than did the wild-type K. pneumoniae at all time points tested. Conversely, overexpression of the wild-type nifX region blocked nif protein synthesis, protein accumulation, and nifHDKTY mRNA accumulation. These complementary results indicate that a product of the nifX region has a role in the negative regulation of nif regulation in response to NH4+ and O2