An oxygen-sensitive toxin-antitoxin system

Nat Commun. 2016 Dec 8;7:13634. doi: 10.1038/ncomms13634.


The Hha and TomB proteins from Escherichia coli form an oxygen-dependent toxin-antitoxin (TA) system. Here we show that YmoB, the Yersinia orthologue of TomB, and its single cysteine variant [C117S]YmoB can replace TomB as antitoxins in E. coli. In contrast to other TA systems, [C117S]YmoB transiently interacts with Hha (rather than forming a stable complex) and enhances the spontaneous oxidation of the Hha conserved cysteine residue to a -SOxH-containing species (sulfenic, sulfinic or sulfonic acid), which destabilizes the toxin. The nuclear magnetic resonance structure of [C117S]YmoB and the homology model of TomB show that the two proteins form a four-helix bundle with a conserved buried cysteine connected to the exterior by a channel with a diameter comparable to that of an oxygen molecule. The Hha interaction site is located on the opposite side of the helix bundle.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • DNA-Binding Proteins / physiology*
  • Escherichia coli K12
  • Escherichia coli Proteins / physiology*
  • Oxidation-Reduction
  • Protein Conformation
  • Toxin-Antitoxin Systems / physiology*
  • Yersinia / chemistry


  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • hha protein, E coli