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Journal of Bacteriology, August 1999, p. 4842-4847, Vol. 181, No. 16
Department of Molecular Biology and
Microbiology, Tufts University School of Medicine, Boston,
Massachusetts 02111
Received 25 February 1999/Accepted 2 June 1999
MppA is a periplasmic binding protein in Escherichia
coli essential for uptake of the cell wall murein tripeptide
L-alanyl-
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
The Periplasmic Murein Peptide-Binding Protein
MppA Is a Negative Regulator of Multiple Antibiotic Resistance
in Escherichia coli
-D-glutamyl-meso-diaminopimelate. We have found serendipitously that E. coli K-12 strains
carrying a null mutation in mppA exhibit increased
resistance to a wide spectrum of antibiotics and to cyclohexane. Normal
sensitivity of the mppA mutant to these agents is restored
by mppA expressed from a plasmid. As is observed in the
multiple antibiotic resistance phenotype in E. coli cells,
the mppA null mutant overproduces the transcriptional
activator, MarA, resulting in expression of the membrane-bound AcrAB
proteins that function as a drug efflux pump. Reduced production of
OmpF similar to that observed in the multiple antibiotic resistance
phenotype is also seen in the mppA mutant. These and other
data reported herein indicate that MppA functions upstream of MarA in a
signal transduction pathway to negatively regulate the expression of
marA and hence of the MarA-driven multiple antibiotic
resistance. Overproduction of cytoplasmic GadA and GadB and of several
unidentified cytoplasmic membrane proteins as well as reduction in the
amount of the outer membrane protein, OmpP, in the mppA
null mutant indicate that MppA regulates a number of genes in addition
to those already known to be controlled by MarA.
*
Corresponding author. Mailing address: Department of
Molecular Biology and Microbiology, Tufts University School of
Medicine, 136 Harrison Ave., Boston, MA 02111. Phone: (617) 636-6753. Fax: (617) 636-0337. E-mail: jpark02{at}emerald.tufts.edu.
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