Affiliation:
1. Department of Biology, Carleton University,Ottawa, Ontario K1S 5B6, Canada
Abstract
ABSTRACT
In
Escherichia coli,
the response to oxidative stress due to elevated levels of superoxide is mediated, in part, by the
soxRS
regulon. One member of the
soxRS
regulon,
nfsA,
encodes the major oxygen-insensitive nitroreductase in
Escherichia coli
which catalyzes the reduction of nitroaromatic and nitroheterocyclic compounds by NADPH. In this study we investigate the regulation of
nfsA
in response to the superoxide generating compound paraquat. The transcription start site (TSS) of
nfsA
was located upstream of the
ybjC
gene, a small open reading frame of unknown function located directly upstream of
nfsA,
suggesting that these two genes form an operon. The activity of the promoter associated with this TSS was confirmed with
lacZ
fusions and was shown to be inducible by paraquat. Footprinting and band shift analysis showed that purified His-tagged SoxS protein binds to a 20-base sequence 10 bases upstream of the −35 promoter sequence in the forward orientation, suggesting that the
ybjC-nfsA
promoter is a class I SoxS-dependent promoter.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
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