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.

Yvonne Göpel,Boris Görke

doi:10.1371/journal.pgen.1007547

Yvonne Göpel, Boris Görke

Open Access

https://doi.org/10.1371/journal.pgen.1007547

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Abstract

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.

Highlights

Two-component systems (TCSs) allow bacteria to perceive information from the environment and to adapt gene expression and behavior in a meaningful way
The enterobacterial two-component system QseE/QseF controls functions related to the cell envelope
We show that QseG is a prerequisite for QseE/QseF activity in E. coli K-12

Summary

Introduction

Two-component systems (TCSs) allow bacteria to perceive information from the environment and to adapt gene expression and behavior in a meaningful way. A membranebound histidine kinase senses a stimulus via its N-terminal input domain leading to autophosphorylation at a histidine residue in the C-terminal transmitter domain [1]. The phosphoryl-group is transferred to an aspartate residue in the receiver domain of the cognate response regulator, thereby activating the associated output domain, which is often a transcription factor. While the downstream functions of many TCSs are well characterized, the stimuli sensed by the kinases and the underlying mechanisms often remain elusive. Histidine kinases may perceive their cognate stimuli directly or through employment of accessory proteins [2,3,4,5]. The model organism E. coli K-12 encodes 29 TCSs, each dedicated to a specific function [6, 7]. YfhK/YfhA), which is conserved in Enterobacteriaceae [8]

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