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Journal of Bacteriology, September 1999, p. 5263-5272, Vol. 181, No. 17
Department of Molecular Biology, Princeton
University, Princeton, New Jersey 08544
Received 9 April 1999/Accepted 8 June 1999
In Escherichia coli, the Cpx two-component regulatory
system activates expression of protein folding and degrading factors in
response to misfolded proteins in the bacterial envelope (inner membrane, periplasm, and outer membrane). It is comprised of the histidine kinase CpxA and the response regulator CpxR. This response plays a role in protection from stresses, such as elevated pH, as well
as in the biogenesis of virulence factors. Here, we show that the Cpx
periplasmic stress response is subject to amplification and repression
through positive and negative autofeedback mechanisms. Western blot and
operon fusion analyses demonstrated that the cpxRA operon
is autoactivated. Conditions that lead to elevated levels of
phosphorylated CpxR cause a concomitant increase in transcription of
cpxRA. Conversely, overproduction of CpxP, a small,
Cpx-regulated protein of previously unknown function, represses the
regulon and can block activation of the pathway. This repression is
dependent on an intact CpxA sensing domain. The ability to autoactivate
and then subsequently repress allows for a temporary amplification of
the Cpx response that may be important in rescuing cells from
transitory stresses and cueing the appropriately timed elaboration of
virulence factors.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
The Cpx Envelope Stress Response Is Controlled by
Amplification and Feedback Inhibition
and
*
Corresponding author. Mailing address: Department of
Molecular Biology, Princeton University, Princeton, NJ 08544. Phone: (609) 258-5899. Fax: (609) 258-2957. E-mail:
tsilhavy{at}molbio.princeton.edu.
Present address: Washington University School of Medicine, St.
Louis, MO 63110.
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