Interaction of lipoprotein QseG with sensor kinase QseE in the periplasm controls the phosphorylation state of the two-component system QseE/QseF in Escherichia coli

PLoS Genet. 2018 Jul 24;14(7):e1007547. doi: 10.1371/journal.pgen.1007547. eCollection 2018 Jul.


Histidine kinase QseE and response regulator QseF compose a two-component system in Enterobacteriaceae. In Escherichia coli K-12 QseF activates transcription of glmY and of rpoE from Sigma 54-dependent promoters by binding to upstream activating sequences. Small RNA GlmY and RpoE (Sigma 24) are important regulators of cell envelope homeostasis. In pathogenic Enterobacteriaceae QseE/QseF are required for virulence. In enterohemorrhagic E. coli QseE was reported to sense the host hormone epinephrine and to regulate virulence genes post-transcriptionally through employment of GlmY. The qseEGF operon contains a third gene, qseG, which encodes a lipoprotein attached to the inner leaflet of the outer membrane. Here, we show that QseG is essential and limiting for activity of QseE/QseF in E. coli K-12. Metabolic 32P-labelling followed by pull-down demonstrates that phosphorylation of the receiver domain of QseF in vivo requires QseE as well as QseG. Accordingly, QseG acts upstream and through QseE/QseF by stimulating activity of kinase QseE. 32P-labelling also reveals an additional phosphorylation in the QseF C-terminus of unknown origin, presumably at threonine/serine residue(s). Pulldown and two-hybrid assays demonstrate interaction of QseG with the periplasmic loop of QseE. A mutational screen identifies the Ser58Asn exchange in the periplasmic loop of QseE, which decreases interaction with QseG and concomitantly lowers QseE/QseF activity, indicating that QseG activates QseE by interaction. Finally, epinephrine is shown to have a moderate impact on QseE activity in E. coli K-12. Epinephrine slightly stimulates QseF phosphorylation and thereby glmY transcription, but exclusively during stationary growth and this requires both, QseE and QseG. Our data reveal a three-component signaling system, in which the phosphorylation state of QseE/QseF is governed by interaction with lipoprotein QseG in response to a signal likely derived from the cell envelope.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Outer Membrane Proteins / metabolism*
  • DNA-Binding Proteins / metabolism*
  • Epinephrine / pharmacology
  • Escherichia coli K12 / physiology*
  • Escherichia coli Proteins / metabolism*
  • Gene Expression Regulation, Bacterial / drug effects
  • Operon / genetics
  • Periplasm / metabolism*
  • Phosphorylation / drug effects
  • Phosphorylation / physiology
  • Promoter Regions, Genetic / genetics
  • Protein Binding / physiology
  • Receptors, Adrenergic / metabolism*
  • Transcription, Genetic / drug effects


  • Bacterial Outer Membrane Proteins
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • QseE protein, E coli
  • QseF protein, E coli
  • Receptors, Adrenergic
  • YfhG protein, E coli
  • Epinephrine

Grants and funding

This work was supported by the ‘Austrian Science Fund’ (FWF; [grant numbers P 26681-B22, F4317 to B.G.]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.