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YeeI, a Novel Protein Involved in Modulation of the Activity of the Glucose-Phosphotransferase System in Escherichia coli K-12

Ann-Katrin Becker, Tim Zeppenfeld, Ariane Staab, Sabine Seitz, Winfried Boos, Teppei Morita, Hiroji Aiba, Kerstin Mahr, Fritz Titgemeyer, and Knut Jahreis^*

Department of Biology and Chemistry, University of Osnabrück, D-49069 Osnabrück, Germany

Received 9 February 2006/ Accepted 1 May 2006

The membrane-bound protein EIICB^Glc encoded by the ptsG gene is the major glucose transporter in Escherichia coli. This protein is part of the phosphoenolpyruvate:glucose-phosphotransferase system, a very important transport and signal transduction system in bacteria. The regulation of ptsG expression is very complex. Among others, two major regulators, the repressor Mlc and the cyclic AMP-cyclic AMP receptor protein activator complex, have been identified. Here we report identification of a novel protein, YeeI, that is involved in the regulation of ptsG by interacting with Mlc. Mutants with reduced activity of the glucose-phosphotransferase system were isolated by transposon mutagenesis. One class of mutations was located in the open reading frame yeeI at 44.1 min on the E. coli K-12 chromosome. The yeeI mutants exhibited increased generation times during growth on glucose, reduced transport of methyl--D-glucopyranoside, a substrate of EIICB^Glc, reduced induction of a ptsG-lacZ operon fusion, and reduced catabolite repression in lactose/glucose diauxic growth experiments. These observations were the result of decreased ptsG expression and a decrease in the amount of EIICB^Glc. In contrast, overexpression of yeeI resulted in higher expression of ptsG, of a ptsG-lacZ operon fusion, and of the autoregulated dgsA gene. The effect of a yeeI mutation could be suppressed by introducing a dgsA deletion, implying that the two proteins belong to the same signal transduction pathway and that Mlc is epistatic to YeeI. By measuring the surface plasmon resonance, we found that YeeI (proposed gene designation, mtfA) directly interacts with Mlc with high affinity.

Present address: Department of Biology, University of Konstanz, D-78457 Konstanz, Germany.

Present address: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.

Present address: Department of Microbiology, University of Erlangen, D-91058 Erlangen, Germany.