Effect of enzyme IIANtr on gene expression in Escherichia coli. Escherichia coli str. K-12 substr. MG1655

Enzyme IIANtr (encoded by ptsN gene) is a component of the nitrogen phosphotransferase system (PTS). It has previously been shown that the dephosphorylated form of EIIANtr is required for the derepression of ilvBN encoding acetohydroxy acid synthase I (AHAS I) catalyzing the first step common to biosynthesis of branched-chain amino acids. Here we examine the effect of deletion of ptsN gene on global gene expression by microarray analysis. Most of the genes down-regulated in a ptsN mutant are controlled by sigma 70, while all the up-regulated genes are controlled by sigma S. As intracellular levels of sigma factors in the ptsN mutant were similar to those of the wild-type strain, this implied that the balance of sigma activities is modified by ptsN deletion. Overall design: The E. coli K12 strain MG1655 and its isogenic ptsN mutant were used in all experiments. Overnight bacterial cultures were incubated in M9 minimal medium containing 0.5% glucose as carbon source. Cells from duplicate experiments were harvested in exponential growth phase when cultures reached an A600 of 0.4. RNA was extracted from each sample using a QIAGEN RNA extraction kit according to the manufacturer's instruction.