title: The positive regulator, TraJ, of the Escherichia coli F plasmid is unstable in a cpxA* background.
abstract: The Cpx (conjugative plasmid expression) stress response of Escherichia coli is induced in response to extracytoplasmic signals generated in the cell envelope, such as misfolded proteins in the periplasm. Detection of stress is mediated by the membrane-bound histidine kinase, CpxA. Signaling of the response regulator CpxR by activated CpxA results in the expression of several factors required for responding to cell envelope stress. CpxA was originally thought to be required for the expression of the positive regulator of the F plasmid transfer (tra) operon, TraJ. It was later determined that constitutive gain-of-function mutations in cpxA led to activation of the Cpx envelope stress response and decreased TraJ expression. In order to determine the nature of the downregulation of TraJ, the level of expression of TraJ, TraM, and TraY, the F-encoded regulatory proteins of the F tra region, was determined both in a cpxA* background and in a wild-type background in which the Cpx stress response was induced by overexpression of the outer membrane lipoprotein, NlpE. Our results suggest that TraJ downregulation is controlled by a posttranscriptional mechanism that operates in the cytoplasm in response to upregulation of the Cpx stress response by both the cpxA* gain-of-function mutation and the overexpression of NlpE.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gubbins
authors.forename: Isabella
authors.initials: I
authors.lastname: Lau
authors.forename: William R
authors.initials: WR
authors.lastname: Will
authors.forename: Janet M
authors.initials: JM
authors.lastname: Manchak
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Raivio
authors.forename: Laura S
authors.initials: LS
authors.lastname: Frost
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003227:Conjugation, Genetic; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins; D005144:F Factor / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C488999:TraJ protein, E coli; C041427:TraJ protein, bacteria; D011494:Protein Kinases; C490475:CpxA protein, E coli; C092472:CpxA protein, bacteria