title: Fnr-, NarP- and NarL-dependent regulation of transcription initiation from the Haemophilus influenzae Rd napF (periplasmic nitrate reductase) promoter in Escherichia coli K-12.
abstract: Periplasmic nitrate reductase (napFDAGHBC operon product) functions in anaerobic respiration. Transcription initiation from the Escherichia coli napF operon control region is activated by the Fnr protein in response to anaerobiosis and by the NarQ-NarP two-component regulatory system in response to nitrate or nitrite. The binding sites for the Fnr and phospho-NarP proteins are centered at positions -64.5 and -44.5, respectively, with respect to the major transcription initiation point. The E. coli napF operon is a rare example of a class I Fnr-activated transcriptional control region, in which the Fnr protein binding site is located upstream of position -60. To broaden our understanding of napF operon transcriptional control, we studied the Haemophilus influenzae Rd napF operon control region, expressed as a napF-lacZ operon fusion in the surrogate host E. coli. Mutational analysis demonstrated that expression required binding sites for the Fnr and phospho-NarP proteins centered at positions -81.5 and -42.5, respectively. Transcription from the E. coli napF operon control region is activated by phospho-NarP but antagonized by the orthologous protein, phospho-NarL. By contrast, expression from the H. influenzae napF-lacZ operon fusion in E. coli was stimulated equally well by nitrate in both narP and narL null mutants, indicating that phospho-NarL and -NarP are equally effective regulators of this promoter. Overall, the H. influenzae napF operon control region provides a relatively simple model for studying synergistic transcription by the Fnr and phospho-NarP proteins acting from class I and class II locations, respectively.
authors.affiliation: Section of Microbiology, University of California, One Shields Avenue, Davis, CA 95616-8665, USA. vjstewart@ucdavis.edu
authors.forename: Valley
authors.initials: V
authors.lastname: Stewart
authors.forename: Peggy J
authors.initials: PJ
authors.lastname: Bledsoe
mesh_terms: D000332:Aerobiosis; D000595:Amino Acid Sequence; D000693:Anaerobiosis; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D048168:Escherichia coli K12 / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005816:Genetic Complementation Test; D006193:Haemophilus influenzae / Q000235:genetics*; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000235:genetics*; D009566:Nitrates / Q000378:metabolism; D009876:Operon / Q000502:physiology; D033903:Periplasmic Proteins / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism; D024363:Transcription Initiation Site / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D007506:Iron-Sulfur Proteins; C491064:ModE protein, E coli; D009566:Nitrates; D033903:Periplasmic Proteins; D014157:Transcription Factors; C081466:narP protein, E coli; C069780:NarL protein, E coli; D009565:Nitrate Reductases; D050901:Nitrate Reductase