Type VI secretion and bacteriophage tail tubes share a common assembly pathway

EMBO Rep. 2014 Mar;15(3):315-21. doi: 10.1002/embr.201337936. Epub 2014 Jan 31.


The Type VI secretion system (T6SS) is a widespread macromolecular structure that delivers protein effectors to both eukaryotic and prokaryotic recipient cells. The current model describes the T6SS as an inverted phage tail composed of a sheath-like structure wrapped around a tube assembled by stacked Hcp hexamers. Although recent progress has been made to understand T6SS sheath assembly and dynamics, there is no evidence that Hcp forms tubes in vivo. Here we show that Hcp interacts with TssB, a component of the T6SS sheath. Using a cysteine substitution approach, we demonstrate that Hcp hexamers assemble tubes in an ordered manner with a head-to-tail stacking that are used as a scaffold for polymerization of the TssB/C sheath-like structure. Finally, we show that VgrG but not TssB/C controls the proper assembly of the Hcp tubular structure. These results highlight the conservation in the assembly mechanisms between the T6SS and the bacteriophage tail tube/sheath.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Secretion Systems*
  • Escherichia coli / chemistry
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / metabolism
  • Molecular Sequence Data
  • Protein Binding
  • Protein Multimerization*
  • Protein Structure, Tertiary
  • Virulence Factors / chemistry*
  • Virulence Factors / metabolism


  • Bacterial Secretion Systems
  • Escherichia coli Proteins
  • HCP1 protein, E coli
  • Virulence Factors