Action at a distance for glp repressor control of glpTQ transcription in Escherichia coli K-12
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Summary
This summary is machine-generated.Escherichia coli glycerol metabolism is regulated by Glp repressor binding to multiple operators within the glpACB and glpTQ operons. Integration host factor (IHF) also plays a role in this regulation, particularly when remote operators are present.
Area Of Science
- Microbiology
- Molecular Biology
- Genetics
Background
- The glpACB and glpTQ operons in Escherichia coli are divergently transcribed and encode key enzymes for anaerobic glycerol metabolism.
- Negative control of these operons is mediated by the glp repressor, which binds to operator sites overlapping the glpA promoter.
Purpose Of The Study
- To investigate the regulatory role of newly identified remote operators (OT1-3) within the glpT coding region.
- To determine the involvement of Integration Host Factor (IHF) in the regulation of glpT expression.
Main Methods
- DNase I footprinting was used to identify IHF binding sites and remote operators.
- A glpT-lacZ transcriptional fusion was constructed to assess the in vivo regulatory effects.
- Site-directed mutagenesis and deletions were employed to inactivate specific operators.
Main Results
- The presence of remote glpT operators significantly increased repression of glpT by the glp repressor (3-4 fold).
- Two IHF binding sites were identified downstream of the glpT transcriptional start site.
- IHF deficiency or mutations reduced glpT repression (2-3 fold), an effect dependent on the presence of remote operators.
Conclusions
- Glp repressor binding to both proximal and remote operators, along with DNA looping facilitated by IHF, contributes to the complex regulation of the glpTQ operon.
- IHF plays a crucial role in enhancing GlpR-mediated repression, particularly when remote operators are involved.