Localisation and protein-protein interactions of the Helicobacter pylori taxis sensor TlpD and their connection to metabolic functions.

Wiebke Behrens,Jonathan L. McMurry,Christine Josenhans,Sarah Menz,Tobias Schweinitzer,Falk F.R. Buettner,Peter C. Loewen

doi:10.1038/srep23582

Abstract

The Helicobacter pylori energy sensor TlpD determines tactic behaviour under low energy conditions and is important in vivo. We explored protein-protein interactions of TlpD and their impact on TlpD localisation and function. Pull-down of tagged TlpD identified protein interaction partners of TlpD, which included the chemotaxis histidine kinase CheAY2, the central metabolic enzyme aconitase (AcnB) and the detoxifying enzyme catalase (KatA). We confirmed that KatA and AcnB physically interact with TlpD. While the TlpD-dependent behavioural response appeared not influenced in the interactor mutants katA and acnB in steady-state behavioural assays, acetone carboxylase subunit (acxC) mutant behaviour was altered. TlpD was localised in a bipolar subcellular pattern in media of high energy. We observed a significant change in TlpD localisation towards the cell body in cheAY2-, catalase- or aconitase-deficient bacteria or in bacteria incubated under low energy conditions, including oxidative stress or respiratory inhibition. Inactivation of tlpD resulted in an increased sensitivity to iron limitation and oxidative stress and influenced the H. pylori transcriptome. Oxidative stress, iron limitation and overexpressing the iron-sulfur repair system nifSU altered TlpD-dependent behaviour. We propose that TlpD localisation is instructed by metabolic activity and protein interactions, and its sensory activity is linked to iron-sulfur cluster integrity.

Highlights

Counterclockwise to clockwise rotation and thereby induce stops, direction changes and backward movements of the bacteria, allowing directed motility[25,26]
We have previously shown that the soluble taxis sensor TlpD, which does not contain transmembrane domains, mediates chemotactic behaviour in response to intrabacterial energy levels in H. pylori[13,26]
The only chemotaxis histidine kinase present in H. pylori, CheAY210,36, which is expected to be interacting with Tlp-orthologous taxis sensors, as previously shown in E. coli[37,38,39], was identified in both experimental repeats (Table 1)

Summary

Introduction

Counterclockwise to clockwise rotation and thereby induce stops, direction changes and backward movements (reversals) of the bacteria, allowing directed motility[25,26]. The H. pylori transmembrane receptor TlpB mediates a repellent response to low pH (< pH 3)[18]; low extracellular pH directly influences the proton motive force of the bacteria[27,28], suggesting a connection between TlpB and energy metabolism. We have previously shown that the soluble taxis sensor TlpD, which does not contain transmembrane domains, mediates chemotactic behaviour in response to intrabacterial energy levels in H. pylori[13,26]. A direct function of protein-protein interactions in chemotaxis or energy taxis might merit further investigations, since a direct impact of NADH dehydrogenase on Aer-mediated sensing in E. coli was discussed[27]. The absence of TlpD induced a shift in global transcript activities These findings indicate a functional connection between the soluble receptor/transducer-like sensor TlpD, its protein-protein interactions and metabolic homeostasis

Methods

Results

Discussion

Conclusion