Affiliation:
1. Department of Biotechnology, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
Abstract
ABSTRACT
The regulatory gene for a σ
54
-dependent-type transcriptional regulator,
fhpR
, is located upstream of the
fhp
gene for flavohemoglobin in
Pseudomonas aeruginosa
. Transcription of
fhp
was induced by nitrate, nitrite, nitric oxide (NO), and NO-generating reagents. Analysis of the
fhp
promoter activity in mutant strains deficient in the denitrification enzymes indicated that the promoter was regulated by NO or related reactive nitrogen species. The NO-responsive regulation was operative in a mutant strain deficient in DNR (dissimilatory nitrate respiration regulator), which is the NO-responsive regulator required for expression of the denitrification genes. A binding motif for σ
54
was found in the promoter region of
fhp
, but an FNR (fumarate nitrate reductase regulator) box was not. The
fhp
promoter was inactive in the
fhpR
or
rpoN
mutant strain, suggesting that the NO-sensing regulation of the
fhp
promoter was mediated by FhpR. The DNR-dependent denitrification promoters (
nirS
,
norC
, and
nosR
) were active in the
fhpR
or
rpoN
mutants. These results indicated that
P. aeruginosa
has at least two independent NO-responsive regulatory systems. The
fhp
or
fhpR
mutant strains showed sensitivity to NO-generating reagents under aerobic conditions but not under anaerobic conditions. These mutants also showed significantly low aerobic NO consumption activity, indicating that the physiological role of flavohemoglobin in
P. aeruginosa
is detoxification of NO under aerobic conditions.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
76 articles.
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