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J Bacteriol. 1997 Jan; 179(1): 228–234.
PMCID: PMC178683

Functional characterization of roles of GalR and GalS as regulators of the gal regulon.

Abstract

An isorepressor of the gal regulon in Escherichia coli, GalS, has been purified to homogeneity. In vitro DNase I protection experiments indicated that among operators of the gal regulon, GalS binds most strongly to the external operator of the mgl operon, which encodes the high-affinity beta-methylgalactoside galactose transport system, and with less affinity to the operators controlling expression of the gal operon, which codes for enzymes of galactose metabolism. GalS has even less affinity for the external operator of galP, which codes for galactose permease, the major low-affinity galactose transporter in the cell. This order of affinities is the reverse of that of GalR, which binds most strongly to the operator of galP and most weakly to that of mgl. Our results also show that GalS, like its homolog, GalR, is a dimeric protein which in binding to the bipartite operators of the gal operon selectively represses its P1 promoter. Consistent with the fact that GalR is the exclusive regulator of the low-affinity galactose transporter, galactose permease, and that the major role of GalS is in regulating expression of the high-affinity galactose transporter encoded by the mgl operon, we found that the DNA binding of GalS is 15-fold more sensitive than that of GalR to galactose.

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Selected References

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  • Aki T, Choy HE, Adhya S. Histone-like protein HU as a specific transcriptional regulator: co-factor role in repression of gal transcription by GAL repressor. Genes Cells. 1996 Feb;1(2):179–188. [PubMed]
  • Brenowitz M, Jamison E, Majumdar A, Adhya S. Interaction of the Escherichia coli Gal repressor protein with its DNA operators in vitro. Biochemistry. 1990 Apr 3;29(13):3374–3383. [PubMed]
  • Boutelje J, Karlström AR, Hartmanis MG, Holmgren E, Sjögren A, Levine RL. Human immunodeficiency viral protease is catalytically active as a fusion protein: characterization of the fusion and native enzymes produced in Escherichia coli. Arch Biochem Biophys. 1990 Nov 15;283(1):141–149. [PubMed]
  • Brown MP, Shaikh N, Brenowitz M, Brand L. The allosteric interaction between D-galactose and the Escherichia coli galactose repressor protein. J Biol Chem. 1994 Apr 29;269(17):12600–12605. [PubMed]
  • Choy HE, Adhya S. Control of gal transcription through DNA looping: inhibition of the initial transcribing complex. Proc Natl Acad Sci U S A. 1992 Dec 1;89(23):11264–11268. [PMC free article] [PubMed]
  • Choy HE, Park SW, Aki T, Parrack P, Fujita N, Ishihama A, Adhya S. Repression and activation of transcription by Gal and Lac repressors: involvement of alpha subunit of RNA polymerase. EMBO J. 1995 Sep 15;14(18):4523–4529. [PMC free article] [PubMed]
  • Golding A, Weickert MJ, Tokeson JP, Garges S, Adhya S. A mutation defining ultrainduction of the Escherichia coli gal operon. J Bacteriol. 1991 Oct;173(19):6294–6296. [PMC free article] [PubMed]
  • Boos W, Lengeler J, Hermann KO, Unsöld HJ. The regulation of the beta-methylgalactoside transport system and of the galactose binding protein of Escherichia coli K12. Eur J Biochem. 1971 Apr 30;19(4):457–470. [PubMed]
  • Royer CA, Chakerian AE, Matthews KS. Macromolecular binding equilibria in the lac repressor system: studies using high-pressure fluorescence spectroscopy. Biochemistry. 1990 May 22;29(20):4959–4966. [PubMed]
  • Studier FW, Moffatt BA. Use of bacteriophage T7 RNA polymerase to direct selective high-level expression of cloned genes. J Mol Biol. 1986 May 5;189(1):113–130. [PubMed]
  • Weickert MJ, Adhya S. Control of transcription of gal repressor and isorepressor genes in Escherichia coli. J Bacteriol. 1993 Jan;175(1):251–258. [PMC free article] [PubMed]
  • Weickert MJ, Adhya S. A family of bacterial regulators homologous to Gal and Lac repressors. J Biol Chem. 1992 Aug 5;267(22):15869–15874. [PubMed]
  • Weickert MJ, Adhya S. The galactose regulon of Escherichia coli. Mol Microbiol. 1993 Oct;10(2):245–251. [PubMed]

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