Gating mechanisms during actin filament elongation by formins

Elife. 2018 Jul 23;7:e37342. doi: 10.7554/eLife.37342.


Formins play an important role in the polymerization of unbranched actin filaments, and particular formins slow elongation by 5-95%. We studied the interactions between actin and the FH2 domains of formins Cdc12, Bni1 and mDia1 to understand the factors underlying their different rates of polymerization. All-atom molecular dynamics simulations revealed two factors that influence actin filament elongation and correlate with the rates of elongation. First, FH2 domains can sterically block the addition of new actin subunits. Second, FH2 domains flatten the helical twist of the terminal actin subunits, making the end less favorable for subunit addition. Coarse-grained simulations over longer time scales support these conclusions. The simulations show that filaments spend time in states that either allow or block elongation. The rate of elongation is a time-average of the degree to which the formin compromises subunit addition rather than the formin-actin complex literally being in 'open' or 'closed' states.

Keywords: FH2 domain; S. cerevisiae; S. pombe; coarse-grained; formin; gating mechanism; intermolecular interactions; molecular biophysics; molecular dynamics; mouse; structural biology.

Publication types

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

MeSH terms

  • Actin Cytoskeleton / chemistry*
  • Actin Cytoskeleton / genetics
  • Actins / chemistry
  • Animals
  • Carrier Proteins / chemistry*
  • Carrier Proteins / genetics
  • Cell Cycle Proteins / chemistry*
  • Cell Cycle Proteins / genetics
  • Crystallography, X-Ray
  • Cytoskeletal Proteins / chemistry*
  • Cytoskeletal Proteins / genetics
  • Cytoskeleton / chemistry
  • Cytoskeleton / genetics
  • Formins
  • Mice
  • Microfilament Proteins / chemistry*
  • Microfilament Proteins / genetics
  • Molecular Dynamics Simulation
  • Multiprotein Complexes / chemistry
  • Protein Binding
  • Protein Conformation
  • Protein Domains / genetics
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae / chemistry
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins / chemistry*
  • Saccharomyces cerevisiae Proteins / genetics


  • Actins
  • Bni1 protein, S cerevisiae
  • CDC12 protein, S cerevisiae
  • Carrier Proteins
  • Cell Cycle Proteins
  • Cytoskeletal Proteins
  • Diap1 protein, mouse
  • Formins
  • Microfilament Proteins
  • Multiprotein Complexes
  • Saccharomyces cerevisiae Proteins