Pathway of Actin Filament Branch Formation by Arp2/3 Complex

J Biol Chem. 2008 Mar 14;283(11):7135-44. doi: 10.1074/jbc.M705894200. Epub 2007 Dec 29.

Abstract

A spectroscopic assay using pyrene-labeled fission yeast Arp2/3 complex revealed that the complex binds to and dissociates from actin filaments extremely slowly with or without the nucleation-promoting factor fission yeast Wsp1-VCA. Wsp1-VCA binds both Arp2/3 complex and actin monomers with high affinity. These two ligands have only modest impacts on the interaction of the other ligand with VCA. Simulations of a mathematical model based on the kinetic parameters determined in this study and elsewhere account for the full time course of actin polymerization in the presence of Arp2/3 complex and Wsp1-VCA and show that an activation step, postulated to follow binding of a ternary complex of Arp2/3 complex, a bound nucleation-promoting factor, and an actin monomer to an actin filament, has a rate constant at least 0.15 s(-1). Kinetic parameters determined in this study constrain the process of actin filament branch formation during cellular motility to one main pathway.

Publication types

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

MeSH terms

  • Actin-Related Protein 2-3 Complex / metabolism*
  • Actins / chemistry*
  • Actins / pharmacology
  • Fluorescence Polarization
  • Fluorescence Resonance Energy Transfer
  • Kinetics
  • Ligands
  • Mass Spectrometry
  • Models, Biological
  • Models, Theoretical
  • Molecular Conformation
  • Mutagenesis
  • Protein Binding
  • Schizosaccharomyces / physiology*
  • Spectrophotometry / methods
  • Time Factors

Substances

  • Actin-Related Protein 2-3 Complex
  • Actins
  • Ligands