Modulation of transcription antitermination in the bgl operon of Escherichia coli by the PTS.
BglG, which regulates expression of the beta-glucoside utilization (bgl) operon in Escherichia coli, represents a family of RNA-binding transcriptional antiterminators that positively regulate transcription of sugar utilization genes in Gram-negative and Gram-positive organisms. BglG is negatively regulated by the beta-glucoside phosphotransferase, BglF, by means of phosphorylation and physical association, and it is positively regulated by the general phosphoenolpyruvate phosphotransferase system (PTS) proteins, enzyme I (EI) and HPr. We studied the positive regulation of BglG both in vitro and in vivo. Here, we show that although EI and HPr are essential for BglG activity, this mode of activation does not require phosphorylation of BglG by HPr, as opposed to the phosphorylation-mediated activation of many BglG-like antiterminators in Gram-positive organisms. The effect of EI and HPr on BglG is not mediated by BglF. Nevertheless, the release of BglG from BglF, which is stimulated by the extracellular sugar in a sugar uptake-independent manner, is a prerequisite for BglG activation. Taken together, the results indicate that activation of BglG is a 2-stage process: a sugar-stimulated release from the membrane-bound sugar sensor followed by a phosphorylation-independent stimulatory effect exerted by the general PTS proteins.
Raveh
Hadas
H
Department of Molecular Biology, The Hebrew University-Hadassah Medical School, PO Box 12272, Jerusalem 91120, Israel.
Lopian
Livnat
L
Nussbaum-Shochat
Anat
A
Wright
Andrew
A
Amster-Choder
Orna
O
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000378:metabolism; D008957:Models, Genetic; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009876:Operon / Q000235:genetics*; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics*; D013728:Terminator Regions, Genetic; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D009004:Monosaccharide Transport Proteins; D016601:RNA-Binding Proteins; C064872:antiterminator proteins, Bacteria; D010770:Phosphotransferases; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C022358:mannitol PTS permease, E coli; C030182:phosphocarrier protein HPr