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J. Bacteriol., Jan 1995, 144-151, Vol 177, No. 1
J Mellies, A Wise and M Villarejo
proP of Escherichia coli encodes an active transport system for proline and
glycine betaine which is activated by both hyperosmolarity and amino
acid-limited growth. proP DNA sequences far upstream from the translational
start site are strongly homologous to the promoter of proU, an operon that
specifies another osmoregulated glycine betaine transport system. Mutation
and deletion analysis of proP and primer extension experiments established
that this promoter, P1, was responsible for proP's strong expression in
minimal medium and its response to osmotic signals. When cells were grown
in complex medium, expression from a proP-lacZ fusion was induced three- to
fourfold as growth slowed and cells entered stationary phase.
Stationary-phase induction was dependent on rpoS, which encodes a
stationary-phase sigma factor. Deletion of 158 bp of the untranslated
leader sequence between P1 and the proP structural gene abolished
rpoS-dependent stationary- phase regulation. Transcription initiation
detected by primer extension within this region was absent in an rpoS
mutant. proP is therefore a member of the growing class of sigma
S-dependent genes which respond to both stationary-phase and
hyperosmolarity signals.
Copyright © 1995, American Society for Microbiology
Two different Escherichia coli proP promoters respond to osmotic and growth phase signals
Section of Microbiology, University of California, Davis 95616.
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