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Escherichia coli K-12 substr. MG1655 Transcription Unit: bglGFB

Local Context (not to scale): ?

Transcription Unit:

Notes: ?

Other Transcription-Units in the Same Operon: bglG (bglGp2) , bglG (bglGp)

Summary:
The bglGFB operon codes for one of four β-glucoside utilization systems in E. coli [Moorthy02]. It codes for the autoregulatory antiterminator BglG, the EII glucoside transporter BglF, and the glucosidase BglB [Schnetz87]. This operon is silent in wild-type cells grown in the lab due to the transcriptional regulator HNS [Yasuzawa92], but it can be activated by insertion of an IS element upstream of the operon, as well as by point mutations within the CRP-binding site or within gyrA or gyrB [Schnetz92, Reynolds81, Reynolds86].

Once the operon is released from its silent state, it can be activated by Crp and repressed by Fis [Gulati00, Caramel00]. The bgl promoter is controlled by σS, whose effect is mediated by Crl [Moorthy02, Schnetz02]. Once silencing ceases, bglGFB expression is controlled by the aromatic β-glucosides salicin and arbutin via an mRNA antitermination mechanism [Schnetz88]. BglG is activated by phosphorylation by HPr (or FPr) but is inactivated by additional phosphorylation by BglF at a different site [Gorke99]. BglG is both phosphorylated and dephosphorylated by BglF, the enzyme II component of the Bgl sugar-transporting phosphotransferase system. The phosphorylation state of BglG at the BglF site is controlled by one of the β-glucoside inducers. In the absence of β-glucoside, BglG associates with and is phosphorylated by BglF in the cytoplasmic membrane. Addition of the inducer leads to dephosphorylation of BglG at the BglF site, and its localization to the cytoplasm where it forms homodimers and its transcriptional antitermination activity allows transcription of the bgl operon. The doubly phosphorylated form of BglG is unable to dimerize and bind to the target mRNA and does not have antiterminator activity [AmsterChoder92, Schnetz90, AmsterChoder90, AmsterChoder89, Lopian03, BenZeev05].

In the absence of the activated BglG homodimer, transcription from the bgl promoter is terminated at one of two rho-independent terminators. The first is located in the leader region of the bgl mRNA at a site immediately upstream of the bglG translation start site, and the second lies between bglG and bglF [Schnetz87, Mahadevan87, Schnetz88]. BglG is able to bind to a site in the bgl mRNA which partially overlaps the rho-independent terminators, possibly blocking the formation of the terminator secondary structure and allowing transcription [Houman90]. BlgG binding stabilizes the 5' end of the bgl mRNA [Gulati01]. BglG also binds the β-subunit of RNA polymerase [NussbaumShochat99].

In addition to these well-established forms of transcriptional regulation, the bgl operon expression is also affected by StpA, Hfq, LeO, and BglJ, but their specific mechanisms remain to be determined [Free98, Tsui94, Ueguchi98, Giel96].

Repression of the bglGFB operon by StpA occurs only in the presence of the N-terminal H-NS protein domain, which comprises the core for dimerization [Gueune08].

Citations: [Schaefler67, Schaefler67a]


Promoter:

Citations: [Reynolds86, Moorthy02, Schnetz02]

Absolute Position of Transcription Start Site: 3904720 base pairs

Position relative to start of first gene (bglG): -130

Sequence:


Site 1 : Bound H-NS (H-NS DNA-binding transcriptional dual regulator) represses transcription. [Dole04, Schnetz96, Ueguchi98, Venkatesh10]

Regulatory Summary: Hns is necessary but is not sufficient for repression of the bglB gene, and it was suggested that other cellular factors are involved in the repression of this gene.

Repression at this site requires the termination factor Rho and is reduced by translation of the bglG mRNA [Dole04].

Position of Site Center Relative to Transcription Start Site (bp): 680

Sequence:

Site Citations: [Dole04]

This site also regulates the following transcription units: bglG (bglGp)


Site 2 : Bound Fis (Fis DNA-binding transcriptional dual regulator) represses transcription. [Caramel00]

Position of Site Center Relative to Transcription Start Site (bp): -27

Sequence:

Site Summary: FIS-site II overlaps the -35 box.

Site Citations: [Caramel00]

This site also regulates the following transcription units: bglG (bglGp)


Site 3 : Bound Fis (Fis DNA-binding transcriptional dual regulator) represses transcription. [Caramel00]

Regulatory Summary: FIS-site I partially overlaps the CAP-binding site.

Position of Site Center Relative to Transcription Start Site (bp): -52

Sequence:

Site Citations: [Caramel00]

This site also regulates the following transcription units: bglG (bglGp)


Site 4 : Bound CRP-cAMP DNA-binding transcriptional dual regulator activates transcription. [Gulati00, Zheng04]

Position of Site Center Relative to Transcription Start Site (bp): -61.5

Sequence:

Site Citations: [Gulati00, Zheng04, Venkatesh10]

This site also regulates the following transcription units: bglG (bglGp) , bglG (bglGp2)


Site 5 : Bound RcsBgl (RcsB-BglJ DNA-binding transcriptional activator) activates transcription. [Madhusudan05, Giel96, Venkatesh10]

Regulatory Summary: BglJ induces bgl operon expression via unknown mechanisms [Giel96, Madhusudan05]. A modest effect was observed on expression of the bglGFB operon during the stationary phase by the BglJ transcriptional regulator in the absence of rpoS/crl [Madan08].

The response regulator RcsB can form heterodimers with RcsA [Kelm97] and GadE [CastanieCornet10] and it forms heterodimers with BglJ to activate the transcription of the bgl operon [Venkatesh10].

The RcsB-BglJ heteromer activates transcription of bglG synergistically with CRP, where it shifts the transcription start by 20 bp from a position typical for class I CRP-dependent promoters (bglGp) to a position typical for class II CRP-dependent promoters (bglGp2) [Salscheider14].

Activation of bglGp2 by RcsB-BglJ is CRP dependent, and the AR2 region of CRP is not involved in coactivation of this promoter by either regulator [Salscheider14]. BglJ-RcsB and CRP synergistically activate the bglGp2 promoter and relieve repression by HNS and StpA.

Position of Site Center Relative to Transcription Start Site (bp): -95.5

Sequence:

Site Citations: [Venkatesh10, Salscheider14]

This site also regulates the following transcription units: bglG (bglGp) , bglG (bglGp2)


Site 6 : Bound LeuO (LeuO DNA-binding transcriptional dual regulator) activates transcription. [Ueguchi98, Venkatesh10]

Regulatory Summary: LeuO can fully antagonize the negative effect of H-NS on the bglGFB operon [Ueguchi98].

Position of Site Center Relative to Transcription Start Site (bp): -118

Sequence:

Site Citations: [Venkatesh10]

This site also regulates the following transcription units: bglG (bglGp)


Site 7 : Bound LeuO (LeuO DNA-binding transcriptional dual regulator) activates transcription. [Ueguchi98, Venkatesh10]

Regulatory Summary: LeuO can fully antagonize the negative effect of H-NS on the bglGFB operon [Ueguchi98].

Position of Site Center Relative to Transcription Start Site (bp): -149

Sequence:

Site Citations: [Venkatesh10]

This site also regulates the following transcription units: bglG (bglGp)


Regulation with unknown or unspecified binding site location:

Bound StpA (H-NS-like DNA-binding protein with RNA chaperone activity) represses transcription. [Gueune08, Venkatesh10]


Attenuation: BglG - his208 phosphorylated prevents premature termination of transcription

Attenuation Type: Protein-Mediated-Attenuation

Terminator Citations: [Schnetz87]

Sequence:


Terminators:
Type Position Relative to Transcription Start Absolute Position Sequence Citations
Rho-Independent 64-105 3904616-3904657 AAAACCUGAC AUAACCAGAG AAUACUGGUG AAGUCGGGUU UU [Schnetz87]
Rho-Independent 4406-4449 3900272-3900315 UUAAUUAUCG UCGCAUUCAG AACAGUCUGG AUGCGAUGCG UUAA [Schnetz87]


References

AmsterChoder89: Amster-Choder O, Houman F, Wright A (1989). "Protein phosphorylation regulates transcription of the beta-glucoside utilization operon in E. coli." Cell 1989;58(5);847-55. PMID: 2673534

AmsterChoder90: Amster-Choder O, Wright A (1990). "Regulation of activity of a transcriptional anti-terminator in E. coli by phosphorylation in vivo." Science 249(4968);540-2. PMID: 2200123

AmsterChoder92: Amster-Choder O, Wright A (1992). "Modulation of the dimerization of a transcriptional antiterminator protein by phosphorylation." Science 257(5075);1395-8. PMID: 1382312

BenZeev05: Ben-Zeev E, Fux L, Amster-Choder O, Eisenstein M (2005). "Experimental and computational characterization of the dimerization of the PTS-regulation domains of BglG from Escherichia coli." J Mol Biol 347(4);693-706. PMID: 15769463

Caramel00: Caramel A, Schnetz K (2000). "Antagonistic control of the Escherichia coli bgl promoter by FIS and CAP in vitro." Mol Microbiol 36(1);85-92. PMID: 10760165

CastanieCornet10: Castanie-Cornet MP, Cam K, Bastiat B, Cros A, Bordes P, Gutierrez C (2010). "Acid stress response in Escherichia coli: mechanism of regulation of gadA transcription by RcsB and GadE." Nucleic Acids Res 38(11);3546-54. PMID: 20189963

Dole04: Dole S, Nagarajavel V, Schnetz K (2004). "The histone-like nucleoid structuring protein H-NS represses the Escherichia coli bgl operon downstream of the promoter." Mol Microbiol 52(2);589-600. PMID: 15066043

Free98: Free A, Williams RM, Dorman CJ (1998). "The StpA protein functions as a molecular adapter to mediate repression of the bgl operon by truncated H-NS in Escherichia coli." J Bacteriol 180(4);994-7. PMID: 9473058

Giel96: Giel M, Desnoyer M, Lopilato J (1996). "A mutation in a new gene, bglJ, activates the bgl operon in Escherichia coli K-12." Genetics 143(2);627-35. PMID: 8725214

Gorke99: Gorke B, Rak B (1999). "Catabolite control of Escherichia coli regulatory protein BglG activity by antagonistically acting phosphorylations." EMBO J 18(12);3370-9. PMID: 10369677

Gueune08: Gueune H, Durand MJ, Thouand G, DuBow MS (2008). "The ygaVP genes of Escherichia coli form a tributyltin-inducible operon." Appl Environ Microbiol 74(6);1954-8. PMID: 18245262

Gulati00: Gulati A, Mahadevan S (2000). "Mechanism of catabolite repression in the bgl operon of Escherichia coli: involvement of the anti-terminator BglG, CRP-cAMP and EIIAGlc in mediating glucose effect downstream of transcription initiation." Genes Cells 5(4);239-50. PMID: 10792463

Gulati01: Gulati A, Mahadevan S (2001). "The Escherichia coli antiterminator protein BglG stabilizes the 5'region of the bgl mRNA." J Biosci 26(2);193-203. PMID: 11426055

Houman90: Houman F, Diaz-Torres MR, Wright A (1990). "Transcriptional antitermination in the bgl operon of E. coli is modulated by a specific RNA binding protein." Cell 62(6);1153-63. PMID: 1698125

Kelm97: Kelm O, Kiecker C, Geider K, Bernhard F (1997). "Interaction of the regulator proteins RcsA and RcsB with the promoter of the operon for amylovoran biosynthesis in Erwinia amylovora." Mol Gen Genet 256(1);72-83. PMID: 9341681

Lopian03: Lopian L, Nussbaum-Shochat A, O'Day-Kerstein K, Wright A, Amster-Choder O (2003). "The BglF sensor recruits the BglG transcription regulator to the membrane and releases it on stimulation." Proc Natl Acad Sci U S A 100(12);7099-104. PMID: 12771379

Madan08: Madan R, Moorthy S, Mahadevan S (2008). "Enhanced expression of the bgl operon of Escherichia coli in the stationary phase." FEMS Microbiol Lett 288(1);131-9. PMID: 18793199

Madhusudan05: Madhusudan S, Paukner A, Klingen Y, Schnetz K (2005). "Independent regulation of H-NS-mediated silencing of the bgl operon at two levels: upstream by BglJ and LeuO and downstream by DnaKJ." Microbiology 151(Pt 10);3349-59. PMID: 16207917

Mahadevan87: Mahadevan S, Wright A (1987). "A bacterial gene involved in transcription antitermination: regulation at a rho-independent terminator in the bgl operon of E. coli." Cell 50(3);485-94. PMID: 3301003

Moorthy02: Moorthy S, Mahadevan S (2002). "Differential spectrum of mutations that activate the Escherichia coli bgl operon in an rpoS genetic background." J Bacteriol 184(14);4033-8. PMID: 12081976

NussbaumShochat99: Nussbaum-Shochat A, Amster-Choder O (1999). "BglG, the transcriptional antiterminator of the bgl system, interacts with the beta' subunit of the Escherichia coli RNA polymerase." Proc Natl Acad Sci U S A 96(8);4336-41. PMID: 10200263

Reynolds81: Reynolds AE, Felton J, Wright A (1981). "Insertion of DNA activates the cryptic bgl operon in E. coli K12." Nature 293(5834);625-9. PMID: 6270569

Reynolds86: Reynolds AE, Mahadevan S, LeGrice SF, Wright A (1986). "Enhancement of bacterial gene expression by insertion elements or by mutation in a CAP-cAMP binding site." J Mol Biol 191(1);85-95. PMID: 3025456

Salscheider14: Salscheider SL, Jahn A, Schnetz K (2014). "Transcriptional regulation by BglJ-RcsB, a pleiotropic heteromeric activator in Escherichia coli." Nucleic Acids Res 42(5);2999-3008. PMID: 24335284

Schaefler67: Schaefler S, Maas WK (1967). "Inducible system for the utilization of beta-glucosides in Escherichia coli. II. Description of mutant types and genetic analysis." J Bacteriol 93(1);264-72. PMID: 5335893

Schaefler67a: Schaefler S (1967). "Inducible system for the utilization of beta-glucosides in Escherichia coli. I. Active transport and utilization of beta-glucosides." J Bacteriol 93(1);254-63. PMID: 5335892

Schnetz02: Schnetz K (2002). "Silencing of the Escherichia coli bgl operon by RpoS requires Crl." Microbiology 148(Pt 8);2573-8. PMID: 12177351

Schnetz87: Schnetz K, Toloczyki C, Rak B (1987). "Beta-glucoside (bgl) operon of Escherichia coli K-12: nucleotide sequence, genetic organization, and possible evolutionary relationship to regulatory components of two Bacillus subtilis genes." J Bacteriol 169(6);2579-90. PMID: 3034860

Schnetz88: Schnetz K, Rak B (1988). "Regulation of the bgl operon of Escherichia coli by transcriptional antitermination." EMBO J 7(10);3271-7. PMID: 2846278

Schnetz90: Schnetz K, Rak B (1990). "Beta-glucoside permease represses the bgl operon of Escherichia coli by phosphorylation of the antiterminator protein and also interacts with glucose-specific enzyme III, the key element in catabolite control." Proc Natl Acad Sci U S A 87(13);5074-8. PMID: 2195546

Schnetz92: Schnetz K, Rak B (1992). "IS5: a mobile enhancer of transcription in Escherichia coli." Proc Natl Acad Sci U S A 1992;89(4);1244-8. PMID: 1311089

Schnetz96: Schnetz K, Wang JC (1996). "Silencing of the Escherichia coli bgl promoter: effects of template supercoiling and cell extracts on promoter activity in vitro." Nucleic Acids Res 24(12);2422-8. PMID: 8710516

Tsui94: Tsui HC, Leung HC, Winkler ME (1994). "Characterization of broadly pleiotropic phenotypes caused by an hfq insertion mutation in Escherichia coli K-12." Mol Microbiol 13(1);35-49. PMID: 7984093

Ueguchi98: Ueguchi C, Ohta T, Seto C, Suzuki T, Mizuno T (1998). "The leuO gene product has a latent ability to relieve bgl silencing in Escherichia coli." J Bacteriol 180(1);190-3. PMID: 9422614

Venkatesh10: Venkatesh GR, Kembou Koungni FC, Paukner A, Stratmann T, Blissenbach B, Schnetz K (2010). "BglJ-RcsB heterodimers relieve repression of the Escherichia coli bgl operon by H-NS." J Bacteriol 192(24);6456-64. PMID: 20952573

Yasuzawa92: Yasuzawa K, Hayashi N, Goshima N, Kohno K, Imamoto F, Kano Y (1992). "Histone-like proteins are required for cell growth and constraint of supercoils in DNA." Gene 122(1);9-15. PMID: 1452042

Zheng04: Zheng D, Constantinidou C, Hobman JL, Minchin SD (2004). "Identification of the CRP regulon using in vitro and in vivo transcriptional profiling." Nucleic Acids Res 32(19);5874-93. PMID: 15520470


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Please cite the following article in publications resulting from the use of EcoCyc: Nucleic Acids Research 41:D605-12 2013
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