Affiliation:
1. Department of Microbiology, Dartmouth Medical School, Hanover, New Hampshire 03755
Abstract
ABSTRACT
The expression of virulence determinants in
Staphylococcus aureus
is controlled by global regulatory loci (e.g.,
sar
and
agr
). The
sar
locus is composed of three overlapping transcripts (
sar
P1, P3, and P2 transcripts from P1, P3, and P2 promoters, respectively), all encoding the 372-bp
sarA
gene. The level of SarA, the major regulatory protein, is partially controlled by the differential activation of
sar
promoters. We previously partially purified a ∼12 kDa protein with a DNA-specific column containing a
sar
P2 promoter fragment. In this study, the putative gene, designated
sarR
, was identified and found to encode a 13.6-kDa protein with homology to SarA. Transcriptional and immunoblot studies revealed the
sarR
gene to be expressed in other staphylococcal strains. Recombinant SarR protein bound
sar
P1, P2, and P3 promoter fragments in gel shift and footprinting assays. A
sarR
mutant expressed a higher level of P1 transcript than the parent, as confirmed by promoter green fluorescent protein fusion assays. As the P1 transcript is the predominant
sar
transcript, we confirmed that the
sarR
mutant expressed more SarA than the parental strain. We thus proposed that SarR is a regulatory protein that binds to the
sar
promoters to down-regulate P1 transcription and the ensuing SarA protein expression.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
114 articles.
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