Potassium mediates Escherichia coli enzyme IIA^Ntr‐dependent regulation of sigma factor selectivity

Abstract

SummaryAn Escherichia coli mutant devoid of enzyme IIA Ntr (EIIA Ntr ) of the nitrogen PTS is extremely sensitive to leucine-containing peptides due to decreased expression of acetohydroxy acid synthase. This decreased expression is due to defective potassium homeostasis. We further elucidate here the mechanism for regulation of gene expression by the intracellular level of K + . The leucine hypersensitivity of a ptsN (encoding EIIA Ntr ) mutant was suppressed by deleting rpoS, encoding the stationary phase s factor. Despite intracellular levels of sigma factors comparable to the wild-type strain, most of the genes downregulated in a ptsN mutant are controlled by s 70 , while all the upregulated genes are controlled by s S , implying that the balance of sigma activities is modified by ptsN deletion. This change of sigma factor activities in the deletion mutant was found to be due to increased levels of K + . In vitro transcription assays demonstrated that a s 70 controlled gene and a s S controlled gene were differentially affected by potassium concentration. Biochemical studies revealed that K + is responsible for sigma factor competition by differentially influencing the binding of s 70 and s S to core RNA polymerase. Taken together, the data suggest that EIIA Ntr controls sigma factor selectivity by regulating the intracellular K + level.

The Emergence of 2-Oxoglutarate as a Master Regulator Metabolite

“…Transcriptome analysis revealed that the expression of many genes is affected by a ptsN deletion, with the most dramatic effect being upregulation of the S regulon (132). It was concluded that K ϩ regulates the selectivity of RNA polymerase toward 70 or S such that, with high K ϩ levels, RNA polymerase preferentially binds S (132).…”

A cAMP-independent carbohydrate-driven mechanism inhibits tnaA expression and TnaA enzyme activity in Escherichia coli

“…However, in the presence of certain carbohydrates the EIIA Ntr protein (encoded by the ptsN gene) is dephosphorylated (Pflüger-Grau & Görke, 2010), and this dephosphorylated product binds to and inhibits the potassium transporter TrkA, which decreases the concentration of intracellular potassium and thus reduces potassium-dependent gene expression (Lee et al, 2007(Lee et al, , 2010. Thus, the presence of glucose might inhibit the enzyme activity of TnaA simply by reducing potassium stores.…”

The Bacterial Phosphoenolpyruvate:Carbohydrate Phosphotransferase System: Regulation by Protein Phosphorylation and Phosphorylation-Dependent Protein-Protein Interactions

“…Indeed, a ptsN mutant accumulates high concentrations of K ϩ inside the cells. K ϩ differentially affects the binding of 70 and S to apo RNA polymerase and thus influences factor selectivity (122). In contrast to EIIA Ntr , phosphorylated EIIA Ntr does not interact with TrkA.…”