Affiliation:
1. Department of Microbiology
2. Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio
3. College of Medicine, University of Illinois at Urbana—Champaign, Urbana, Illinois
Abstract
ABSTRACT
Salmonella enterica
serovar Typhimurium has two manganese transport systems, MntH and SitABCD. MntH is a bacterial homolog of the eukaryotic natural resistance-associated macrophage protein 1 (Nramp1), and SitABCD is an ABC-type transporter. Previously we showed that
mntH
is negatively controlled at the transcriptional level by the
trans
-acting regulatory factors, MntR and Fur. In this study, we examined the transcriptional regulation of
sitABCD
and compared it to the transcriptional regulation of
mntH
by constructing
lacZ
fusions to the promoter regions with and without mutations in putative MntR and/or Fur binding sites. The presence of Mn caused transcriptional repression of the
sitABCD
and
mntH
promoters primarily via MntR, but Fur was also capable of some repression in response to Mn. Likewise, Fe in the medium repressed transcription of both
sit
and
mntH
primarily via Fur, although MntR was also involved in this response. Transcriptional control by MntR and Fur was disrupted by site-specific mutations in the putative MntR and Fur binding sites, respectively. Transcription of the
sit
operon was also affected by the oxygen level and growth phase, but the increased expression observed under high oxygen conditions and higher cell densities is consistent with decreased availability of metals required for repression by the metalloregulatory proteins.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
83 articles.
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