Requirement of the dephospho-form of enzyme IIANtr for derepression of Escherichia coli K-12 ilvBN expression

Abstract

While the proteins of the phosphoenolpyruvate:carbohydrate phosphotransferase system (carbohydrate PTS) have been shown to regulate numerous targets, little such information is available for the nitrogen-metabolic phosphotransferase system (nitrogen-metabolic PTS). To elucidate the physiological role of the nitrogen-metabolic PTS, we carried out phenotype microarray (PM) analysis with Escherichia coli K-12 strain MG1655 deleted for the ptsP gene encoding the first enzyme of the nitrogen-metabolic PTS. Together with the PM data, growth studies revealed that a ptsN (encoding enzyme IIANtr) mutant became extremely sensitive to leucine-containing peptides (LCPs), while both ptsP (encoding enzyme I Ntr) and ptsO (encoding NPr) mutants were more resistant than wild type. The toxicity of LCPs was found to be due to leucine and the dephospho-form of enzyme IIANtr was found to be necessary to neutralize leucine toxicity. Further studies showed that the dephospho-form of enzyme IIA Ntr is required for derepression of the ilvBN operon encoding acetohydroxy acid synthase I catalysing the first step common to the biosynthesis of the branched-chain amino acids. © 2005 Blackwell Publishing Ltd.