Signal transduction between a membrane-bound transporter, PtsG, and a soluble transcription factor, Mlc, of Escherichia coli.
The global regulator Mlc controls several genes implicated in sugar utilization systems, notably the phosphotransferase system (PTS) genes, ptsG, manXYZ and ptsHI, as well as the malT activator. No specific low molecular weight inducer has been identified that can inactivate Mlc, but its activity appeared to be modulated by transport of glucose via Enzyme IICB(Glc) (PtsG). Here we demonstrate that inactivation of Mlc is achieved by sequestration of Mlc to membranes containing dephosphorylated Enzyme IICB(Glc). We show that Mlc binds specifically to membrane fractions which carry PtsG and that excess Mlc can inhibit Enzyme IICB(Glc) phosphorylation by the general PTS proteins and also Enzyme IICB(Glc)-mediated phosphorylation of alpha-methylglucoside. Binding of Mlc to Enzyme IICB(Glc) in vitro required the IIB domain and the IIC-B junction region. Moreover, we show that these same regions are sufficient for Mlc regulation in vivo, via cross-dephosphorylation of IIB(Glc) during transport of other PTS sugars. The control of Mlc activity by sequestration to a transport protein represents a novel form of signal transduction in gene regulation.
Lee
S J
SJ
Department of Biology, University of Konstanz, D-78457 Konstanz, Germany.
Boos
W
W
Bouché
J P
JP
Plumbridge
J
J
D001426:Bacterial Proteins / Q000378:metabolism; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008757:Methylglucosides / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D009875:Operator Regions, Genetic / Q000235:genetics; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000378:metabolism*; D015398:Signal Transduction; D012995:Solubility; D014157:Transcription Factors / Q000378:metabolism*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D008757:Methylglucosides; C111065:Mlc protein, E coli; D012097:Repressor Proteins; D014157:Transcription Factors; C027020:methylglucoside; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C031629:phosphoenolpyruvate-glucose phosphotransferase