Identification of a nitrogen-regulated promoter controlling expression of Klebsiella pneumoniae urease genes.
Synthesis of urease by Klebsiella species is known to be induced when the nitrogen source of the growth medium is limiting, suggesting that urease gene expression is controlled by the nitrogen regulatory (ntr) system. This study showed that K. pneumoniae with mutations in either ntrA or ntrC, two integral components of the ntr system, were phenotypically urease-negative. These mutants could be complemented back to a urease positive phenotype with recombinant plasmids encoding the corresponding ntr gene. A series of ure-lacZYA transcriptional fusions, in conjunction with primer extension analysis, identified a DNA region that encoded a nitrogen-regulated promoter. This promoter region controlled transcription of ureD, the first gene in the Klebsiella pneumoniae urease gene cluster, and ureA, a gene that resides immediately downstream of ureD. A high level of transcription from the ureD promoter required NAC, a recently characterized member of the nitrogen regulatory cascade. NAC is a Lys R-like transcriptional regulator that can act at sigma 70 promoters; expression from nac itself is dependent upon NTRA. Therefore, expression of K. pneumoniae urease was dependent upon the nitrogen regulatory cascade, and transcription of at least two urease genes was from a promoter that was positively regulated by NAC.
Department of Microbiology and Immunology, University of Miami School of Medicine, Florida 33101.
C M
CM
Collins
D M
DM
Gutman
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H
Laman
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005798:Genes, Bacterial; D007711:Klebsiella pneumoniae / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D015398:Signal Transduction; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic; D014510:Urease / Q000096:biosynthesis* / Q000235:genetics
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C072712:NAC protein, bacteria; D014157:Transcription Factors; D014510:Urease; D009584:Nitrogen