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| The EMBO Journal
(2000) 19, 5353–5361, doi:10.1093/emboj/19.20.5353 |
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| Signal transduction between a membrane-bound transporter, PtsG, and a soluble transcription factor, Mlc, of Escherichia coli |
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| Sung-Jae Lee1, Winfried Boos1, Jean-Pierre Bouché2 and Jacqueline Plumbridge3 |
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1 Department of Biology, University of Konstanz, D-78457 Konstanz, Germany 2 Laboratoire de Microbiologie et de la Génétique Moléculaire du CNRS (UMR5100), 118 route de Narbonne, 31062 Toulouse, France 3 Institut de Biologie Physico-Chimique (UPR9073), 13 rue Pierre et Marie Curie, 75005 Paris, France To whom correspondence should be addressed Jacqueline Plumbridge, plumbridge@ibpc.fr Received 28 June 2000; Revised 14 August 2000; Accepted 16 August 2000. |
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| Abstract |
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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 IICBGlc (PtsG). Here we demonstrate that inactivation of Mlc is achieved by sequestration of Mlc to membranes containing dephosphorylated Enzyme IICBGlc. We show that Mlc binds specifically to membrane fractions which carry PtsG and that excess Mlc can inhibit Enzyme IICBGlc phosphorylation by the general PTS proteins and also Enzyme IICBGlc-mediated phosphorylation of  -methylglucoside. Binding of Mlc to Enzyme IICBGlc 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 IIBGlc 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. |
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| Keywords: glucose transport, induction, PTS, repressor sequestration |
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