Actin filament assembly by bacterial factors VopL/F: Which end is up?

Abstract

Competing models have been proposed for actin filament nucleation by the bacterial proteins VopL/F. In this issue, Burke et al. (2017. J. Cell Biol. https ://doi .org /10 .1083 / jcb .201608104) use direct observation to demonstrate that VopL/F bind the barbed and pointed ends of actin filaments but only nucleate new filaments from the pointed end.