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The nitrogen fixation (nif) genes of Klebsiella pneumoniae are specifically regulated by the products of the nifLA operon. We have located the promoter of this operon, and identified sequences required for nifLA transcription. Transcription from this promoter is shown to be positively regulated by the ntrC gene product (which coordinates the expression of(More)
Biological nitrogen fixation is a complex process requiring multiple genes working in concert. To date, the Klebsiella pneumoniae nif gene cluster, divided into seven operons, is one of the most studied systems. Its nitrogen fixation capacity is subject to complex cascade regulation and physiological limitations. In this report, the entire K. pneumoniae nif(More)
Nitric oxide (NO), synthesized in eukaryotes by the NO synthases, has multiple roles in signalling pathways and in protection against pathogens. Pathogenic microorganisms have apparently evolved defence mechanisms that counteract the effects of NO and related reactive nitrogen species. Regulatory proteins that sense NO mediate the primary response to NO and(More)
Most biological nitrogen fixation is catalyzed by molybdenum-dependent nitrogenase, an enzyme complex comprising two component proteins that contains three different metalloclusters. Diazotrophs contain a common core of nitrogen fixation nif genes that encode the structural subunits of the enzyme and components required to synthesize the metalloclusters.(More)
The bacterial activator protein NorR binds to enhancer-like elements, upstream of the promoter site, and activates sigma(54)-dependent transcription of genes that encode nitric oxide detoxifying enzymes (NorVW), in response to NO stress. Unique to the norVW promoter in Escherichia coli is the presence of three enhancer sites associated with a binding site(More)
The transposons Tn5, Tn7 and Tn10 and bacteriophage Mu have been used to derive insertion mutations in the Klebsiella pneumoniae nif gene cluster. A large number of deletion mutants have been derived by imprecise excision of insertion mutations and these deletions have been used to construct a fine-structure map of the nif cluster. Comparison of this(More)
The regulatory protein NsrR, a member of the Rrf2 family of transcription repressors, is specifically dedicated to sensing nitric oxide (NO) in a variety of pathogenic and non-pathogenic bacteria. It has been proposed that NO directly modulates NsrR activity by interacting with a predicted [Fe-S] cluster in the NsrR protein, but no experimental evidence has(More)