Affiliation:
1. Section of Microbiology, University of California, Davis, California 95616
Abstract
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.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
16 articles.
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