AI Article Synopsis
- The bgl operon in E. coli is activated by beta-glucosides through the action of BglG, which prevents early transcription termination by binding to the bgl transcript when it dimerizes.
- BglG's dimerization and function are regulated by BglF, a membrane enzyme that alters BglG's phosphorylation state depending on beta-glucoside levels.
- Recent findings indicate that BglG can exist in a compact monomeric form with its two regulatory domains (PRD1 and PRD2) close together, suggesting a conformational change is crucial during its transition to the dimeric state to effectively regulate operon expression.
Article Abstract
Expression of the bgl operon in Escherichia coli, induced by beta-glucosides, is positively regulated by BglG, a transcriptional antiterminator. In the presence of inducer, BglG dimerizes and binds to the bgl transcript to prevent premature termination of transcription. The dimeric state of BglG is determined by BglF, a membrane-bound enzyme II of the phosphoenolpyruvate-dependent phosphotransferase system (PTS), which reversibly phosphorylates BglG according to beta-glucoside availability. BglG is composed of an RNA-binding domain followed by two homologous PTS regulation domains (PRD1 and PRD2). The predicted structure of dimeric LicT, a BglG homologue from Bacillus subtilis, suggests that the two PRDs adopt a similar structure and that the interactions within the dimer are PRD1-PRD1 and PRD2-PRD2. We have shown recently that the PRD1 and PRD2 domains of BglG can form a stable heterodimer. We report here, based on in vitro and in vivo cross-linking experiments, that a fraction of BglG is present in the cell in a compact form in which PRD1 and PRD2 are in close proximity. The compact form is present mainly in the BglG monomers. Our results imply that the monomer-dimer transition involves a conformational change. The possible role of the compact form in preventing untimely induction of the bgl operon is discussed.
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| http://dx.doi.org/10.1074/jbc.M308085200 | DOI Listing |
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