Identification of a novel genetic locus involved in the regulation of ptsG expression in Escherichia coli

Abstract

The phosphoenolpyruvate-dependent carbohydrate phosphotransferase system (PTS) is responsible for the simultaneous transfer and phosphorylation of various carbon sources in Escherichia coli. The ptsG gene encoding enzyme IICBGlc, the membrane component of the glucose-specific PTS, is repressed by Mlc and activated by CRP?cAMP complex. In addition, it has been reported that various other factors are involved in the ptsG regulation such as heat shock RNA polymerase, Fis, FruR, ArcA and mRNA degradation. In an attempt to discover a novel gene taking part in the regulation of ptsG, a mutant whose ptsG transcription decreased in the presence of glucose compared with the wild type strain was selected after random mutagenesis using transposon Tn10. As a result of sequencing the PCR product amplified with a random primer annealing to the chromosome in the vicinity of the transposon and a transposon-specific primer, yhjV was found to bear the transposon. Furthermore, global gene expression in the mutant was monitored employing DNA microarray technology to understand its function related to the ptsG regulation. It has been found that ptsG expression decreased in spite of the factors contributing to the activation of ptsG such as the promotion of unphosphorylation of EIICBGlc and derepression of Mlc stemmed from reduced PEP and down-regulation of ArcA, one of the repressors of ptsG. These findings strongly suggest that YhjV acts as an activator of ptsG.