ClpAP protease is a universal factor that activates the parDE toxin-antitoxin system from a broad host range RK2 plasmid

Andrzej Dubiel,Adam P Kupinski,Katarzyna Wegrzyn,Igor Konieczny

doi:10.1038/s41598-018-33726-y

Andrzej Dubiel, Adam P Kupinski + Show 2 more

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https://doi.org/10.1038/s41598-018-33726-y

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Abstract

The activity of type II toxin-antitoxin systems (TA), which are responsible for many important features of bacterial cells, is based on the differences between toxin and antitoxin stabilities. The antitoxin lability results from bacterial protease activity. Here, we investigated how particular Escherichia coli cytosolic proteases, namely, Lon, ClpAP, ClpXP, and ClpYQ, affect the stability of both the toxin and antitoxin components of the parDE system from the broad host range plasmid RK2. The results of our in vivo and in vitro experiments show that the ParD antitoxin is degraded by the ClpAP protease, and dsDNA stimulates this process. The ParE toxin is not degraded by any of these proteases and can therefore cause growth inhibition of plasmid-free cells after an unequal plasmid distribution during cell division. We also demonstrate that the ParE toxin interaction with ParD prevents antitoxin proteolysis by ClpAP; however, this interaction does not prevent the ClpAP interaction with ParD. We show that ClpAP protease homologs affect plasmid stability in other bacterial species, indicating that ClpAP is a universal activator of the parDE system and that ParD is a universal substrate for ClpAP.

Highlights

Toxin-antitoxin systems (TA) are widely distributed among prokaryotes
In strains with inactive clpA genes, no statistically significant difference in the stability of the plasmids was observed (Fig. 6, Supplementary Table S4). These results clearly indicate that the ClpAP protease is responsible for maintaining the plasmid that contains the parDE system in different bacterial species
Antitoxin stability has been examined in many E. coli toxin-antitoxin systems (TA) systems using in vivo analysis, yet little is known about antitoxin stability in other bacteria species

Summary

Introduction

Toxin-antitoxin systems (TA) are widely distributed among prokaryotes. Until now, homologous systems in eukaryotes have not been identified[1]. Literature reports demonstrate that plasmidic TA systems can contribute to effects comparable to the chromosomal TA systems in host cells and affect the response to environmental stress. The vapBC TA module from the plasmid pSLT confers Salmonella Typhimurium virulence and stabilizes the virulence plasmid of this species[15,16] These observations make plasmidic TA systems more intriguing, since they provide basic maintenance functions of the plasmid DNA but the host cell may benefit under stress conditions. Formation of the toxin-antitoxin complex results in inhibition of toxin activity towards a cellular target. These complexes are often responsible for the autoregulation of www.nature.com/scientificreports/. ParE alters gyrase activity, which results in DNA nicking and the formation of improper linear forms of chromosomal DNA36. The protease responsible for degrading the ParD antitoxin of the parDE system has not been identified

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