ParE toxin encoded by the broad-host-range plasmid RK2 is an inhibitor of Escherichia coli gyrase

Mol Microbiol. 2002 May;44(4):971-9. doi: 10.1046/j.1365-2958.2002.02921.x.


Broad-host-range plasmid RK2 encodes a post-segregational killing system, parDE, which contributes to the stable maintenance of this plasmid in Escherichia coli and many distantly related bacteria. The ParE protein is a toxin that inhibits cell growth, causes cell filamentation and eventually cell death. The ParD protein is a specific ParE antitoxin. In this work, the in vitro activities of these two proteins were examined. The ParE protein was found to inhibit DNA synthesis using an E. coli oriC supercoiled template and a replication-proficient E. coli extract. Moreover, ParE inhibited the early stages of both chromosomal and plasmid DNA replication, as measured by the DnaB helicase- and gyrase-dependent formation of FI*, a highly unwound form of supercoiled DNA. The presence of ParD prevented these inhibitory activities of ParE. We also observed that the addition of ParE to supercoiled DNA plus gyrase alone resulted in the formation of a cleavable gyrase-DNA complex that was converted to a linear DNA form upon addition of sodium dodecyl sulphate (SDS). Adding ParD before or after the addition of ParE prevented the formation of this cleavable complex. These results demonstrate that the target of ParE toxin activity in vitro is E. coli gyrase.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Bacterial Proteins / metabolism
  • Bacterial Proteins / pharmacology
  • Bacterial Toxins / antagonists & inhibitors
  • Bacterial Toxins / genetics*
  • Bacterial Toxins / metabolism*
  • Bacterial Toxins / pharmacology
  • DNA Gyrase / metabolism
  • DNA Replication / drug effects
  • DNA-Binding Proteins / antagonists & inhibitors
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • DNA-Binding Proteins / pharmacology
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli Proteins*
  • Plasmids / genetics*
  • R Factors / genetics
  • Replication Origin / genetics
  • Topoisomerase II Inhibitors*


  • Bacterial Proteins
  • Bacterial Toxins
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • ParD protein, E coli
  • ParD protein, Plasmid RK2
  • Topoisomerase II Inhibitors
  • parD protein, Bacteria
  • Adenosine Triphosphate
  • DNA Gyrase