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Two Extracytoplasmic Function Sigma Subunits, ςE and ςFecI, of Escherichia coli: Promoter Selectivity and Intracellular Levels

By Hiroto Maeda, Miki Jishage, Tasuku Nomura, Nobuyuki Fujita and Akira Ishihama

Abstract

The promoter selectivity of two extracytoplasmic function (ECF) subfamily ς subunits, ςE (ς24) and ςFecI (ς18), of Escherichia coli RNA polymerase was analyzed by using an in vitro transcription system and various promoters. The EςE holoenzyme recognized only the known cognate promoters, rpoEP2, rpoHP3, and degP, and the EςFecI recognized only one known cognate promoter, fecA. The strict promoter recognition properties of ςE and ςFecI are similar to those of other minor ς subunits. Transcription by EςE and EςFecI was enhanced by high concentrations of glutamate, as in the case of other minor ς subunits. The optimum temperature for transcription by EςFecI was low, around 25°C, apparently in agreement with the high rate of iron sequestration by E. coli at low temperatures. By quantitative Western blot analysis, the intracellular levels of ςE and ςFecI in the uninduced steady-state culture of E. coli W3110 (type A) were determined to be 0.7 to 2.0 and 0.1 to 0.2 fmol per μg of total proteins (or 3 to 9 and 0.4 to 0.9 molecules per cell), respectively, and less than 1% of the level of the major ς70 subunit

Topics: Genetics and Molecular Biology
Publisher: American Society for Microbiology
Year: 2000
OAI identifier: oai:pubmedcentral.nih.gov:94400
Provided by: PubMed Central
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