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Potassium mediates Escherichia coli enzyme IIA Ntr ‐dependent regulation of sigma factor selectivity
Author(s) -
Lee ChangRo,
Cho SeungHyon,
Kim HyunJin,
Kim Miri,
Peterkofsky Alan,
Seok YeongJae
Publication year - 2010
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07419.x
Subject(s) - sigma factor , rpos , mutant , biology , intracellular , escherichia coli , microbiology and biotechnology , gene , gene expression , rna polymerase , biochemistry , enzyme , promoter
Summary An 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 σ 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 σ 70 , while all the upregulated genes are controlled by σ 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 σ 70 controlled gene and a σ 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 σ 70 and σ S to core RNA polymerase. Taken together, the data suggest that EIIA Ntr controls sigma factor selectivity by regulating the intracellular K + level.