title: Characterization of MtfA, a novel regulatory output signal protein of the glucose-phosphotransferase system in Escherichia coli K-12.
abstract: The glucose-phosphotransferase system (PTS) in Escherichia coli K-12 is a complex sensory and regulatory system. In addition to its central role in glucose uptake, it informs other global regulatory networks about carbohydrate availability and the physiological status of the cell. The expression of the ptsG gene encoding the glucose-PTS transporter EIICB(Glc) is primarily regulated via the repressor Mlc, whose inactivation is glucose dependent. During transport of glucose and dephosphorylation of EIICB(Glc), Mlc binds to the B domain of the transporter, resulting in derepression of several Mlc-regulated genes. In addition, Mlc can also be inactivated by the cytoplasmic protein MtfA in a direct protein-protein interaction. In this study, we identified the binding site for Mlc in the carboxy-terminal region of MtfA by measuring the effect of mutated MtfAs on ptsG expression. In addition, we demonstrated the ability of MtfA to inactivate an Mlc super-repressor, which cannot be inactivated by EIICB(Glc), by using in vivo titration and gel shift assays. Finally, we characterized the proteolytic activity of purified MtfA by monitoring cleavage of amino 4-nitroanilide substrates and show Mlc's ability to enhance this activity. Based on our findings, we propose a model of MtfA as a glucose-regulated peptidase activated by cytoplasmic Mlc. Its activity may be necessary during the growth of cultures as they enter the stationary phase. This proteolytic activity of MtfA modulated by Mlc constitutes a newly identified PTS output signal that responds to changes in environmental conditions.
authors.affiliation: Department of Biology and Chemistry, University of Osnabrück, Osnabrück, Germany.
authors.forename: Anna-Katharina
authors.initials: AK
authors.lastname: Göhler
authors.forename: Ariane
authors.initials: A
authors.lastname: Staab
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Gabor
authors.forename: Karina
authors.initials: K
authors.lastname: Homann
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Klang
authors.forename: Anne
authors.initials: A
authors.lastname: Kosfeld
authors.forename: Janna-Eleni
authors.initials: JE
authors.lastname: Muus
authors.forename: Jana Selina
authors.initials: JS
authors.lastname: Wulftange
authors.forename: Knut
authors.initials: K
authors.lastname: Jahreis
mesh_terms: D001665:Binding Sites; D024202:Electrophoretic Mobility Shift Assay; D048168:Escherichia coli K12 / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism*; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000096:biosynthesis*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D012097:Repressor Proteins / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; C111065:Mlc protein, E coli; D012097:Repressor Proteins; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C031629:phosphoenolpyruvate-glucose phosphotransferase; D010447:Peptide Hydrolases