Characterization of MtfA, a Novel Regulatory Output Signal Protein of the Glucose-Phosphotransferase System in Escherichia coli K-12

Autor(en): Goehler, Anna-Katharina
Staab, Ariane
Gabor, Elisabeth
Homann, Karina
Klang, Elisabeth
Kosfeld, Anne
Muus, Janna-Eleni
Wulftange, Jana Selina
Jahreis, Knut
Stichwörter: ANTHRAX LETHAL FACTOR; EXPRESSION; GLOBAL REPRESSOR MLC; IICBGLC; INACTIVATION; MEMBRANE SEQUESTRATION; Microbiology; PHOSPHORYLATION; PTSG; TRANSCRIPTION; TRANSPORTER
Erscheinungsdatum: 2012
Herausgeber: AMER SOC MICROBIOLOGY
Journal: JOURNAL OF BACTERIOLOGY
Volumen: 194
Ausgabe: 5
Startseite: 1024
Seitenende: 1035
Zusammenfassung: 
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 EIICBGlc is primarily regulated via the repressor Mlc, whose inactivation is glucose dependent. During transport of glucose and dephosphorylation of ElICB(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 EIICBGlc, 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.
ISSN: 00219193
DOI: 10.1128/JB.06387-11

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