Journal of Bacteriology, September 1998, p. 4406-4412, Vol. 180, No. 17
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Laboratoire des Enveloppes Bactériennes, Centre National de la Recherche Scientifique, Université Paris-Sud, 91405 Orsay Cedex, France1; Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigationes Científicas, Universidad Autónoma de Madrid, Canto Blanco, 28049 Madrid, Spain2; and National Institute of Genetics, Mishima, Shizuoka-ken 411, Japan3
Received 7 May 1998/Accepted 1 July 1998
Recently, a promoter for the essential gene ftsI, which
encodes penicillin-binding protein 3 of Escherichia coli,
was precisely localized 1.9 kb upstream from this gene, at the
beginning of the mra cluster of cell division and cell
envelope biosynthesis genes (H. Hara, S. Yasuda, K. Horiuchi, and
J. T. Park, J. Bacteriol. 179:5802-5811, 1997). Disruption of
this promoter (Pmra) on the chromosome and its
replacement by the lac promoter
(Pmra::Plac) led to isopropyl-
-D-thiogalactopyranoside
(IPTG)-dependent cells that lysed in the absence of inducer, a defect
which was complemented only when the whole region from
Pmra to ftsW, the fifth gene
downstream from ftsI, was provided in trans on
a plasmid. In the present work, the levels of various proteins involved
in peptidoglycan synthesis and cell division were precisely determined in cells in which
Pmra::Plac
promoter expression was repressed or fully induced. It was confirmed
that the Pmra promoter is required for
expression of the first nine genes of the mra cluster:
mraZ (orfC), mraW
(orfB), ftsL (mraR),
ftsI, murE, murF, mraY,
murD, and ftsW. Interestingly, three- to
sixfold-decreased levels of MurG and MurC enzymes were observed in
uninduced
Pmra::Plac cells. This was correlated with an accumulation of the nucleotide precursors UDP-N-acetylglucosamine and
UDP-N-acetylmuramic acid, substrates of these enzymes, and
with a depletion of the pool of UDP-N-acetylmuramyl
pentapeptide, resulting in decreased cell wall peptidoglycan synthesis.
Moreover, the expression of ftsZ, the penultimate gene from
this cluster, was significantly reduced when
Pmra expression was repressed. It was concluded that the transcription of the genes located downstream from
ftsW in the mra cluster, from murG
to ftsZ, is also mainly (but not exclusively) dependent on
the Pmra promoter.
Present address: Department of Biochemistry and Molecular Biology,
Saitama University, Urawa, Saitama 338-8570, Japan.
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