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J. Bacteriol., 09 1995, 4980-4984, Vol 177, No. 17
AC Ghrist and GV Stauffer
The Escherichia coli glycine cleavage enzyme system catalyzes the cleavage
of glycine, generating CO2, NH3, and a one-carbon unit. Expression of the
operon encoding this enzyme system (gcv) is induced in the presence of
glycine and repressed in the presence of purines. In this study, a mutant
with high-level constitutive expression of a gcvT- lacZ gene fusion was
isolated. The mutation in this strain was designated gcvR1 and was mapped
to min 53.3 on the E. coli chromosome. A single-copy plasmid carrying the
wild-type gcvR gene complemented the mutation, restoring normal regulation
of a gcvT-lacZ fusion, while a multicopy plasmid carrying gcvR led to
superrepression under all growth conditions. Negative regulation of a
gcvT-lacZ fusion by GcvR was shown to require GcvA, a LysR family protein
known to both activate gcv in the presence of glycine and repress gcv in
the presence of purines. Models explaining how GcvR and GcvA might interact
to regulate gcv expression are proposed.
Copyright © 1995, American Society for Microbiology
Characterization of the Escherichia coli gcvR gene encoding a negative regulator of gcv expression
Department of Microbiology, University of Iowa, Iowa City 52242, USA.
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