The bacterial virulence factors VopL and VopF nucleate actin from the pointed end

J Cell Biol. 2017 May 1;216(5):1267-1276. doi: 10.1083/jcb.201608104. Epub 2017 Mar 31.


VopL and VopF (VopL/F) are tandem WH2-domain actin assembly factors used by infectious Vibrio species to induce actin assembly in host cells. There is disagreement about the filament assembly mechanism of VopL/F, including whether they associate with the filament barbed or pointed end. Here, we used multicolor total internal reflection fluorescence microscopy to directly observe actin assembly with fluorescently labeled VopL/F. In actin monomer assembly reactions, VopL/F exclusively nucleate actin filament assemblies, remaining only briefly associated with the pointed end. VopL/F do not associate with the ends of preassembled filaments. In assembly reactions with saturating profilin, ∼85% of VopL/F molecules also promote nucleation from the pointed end, whereas a smaller fraction (<15%) associate for ∼25 s with the barbed end of preassembled filaments, inhibiting their elongation. We conclude that VopL/F function primarily as actin nucleation factors that remain briefly (∼100 s) associated with the pointed end.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actins / chemistry*
  • Actins / metabolism*
  • Bacterial Proteins / isolation & purification
  • Bacterial Proteins / metabolism*
  • Polymerization
  • Vibrio / metabolism*
  • Virulence Factors / isolation & purification
  • Virulence Factors / metabolism*


  • Actins
  • Bacterial Proteins
  • Virulence Factors