Insights into the influence of nucleotides on actin family proteins from seven structures of Arp2/3 complex

Mol Cell. 2007 May 11;26(3):449-57. doi: 10.1016/j.molcel.2007.04.017.


ATP is required for nucleation of actin filament branches by Arp2/3 complex, but the influence of ATP binding and hydrolysis are poorly understood. We determined crystal structures of bovine Arp2/3 complex cocrystallized with various bound adenine nucleotides and cations. Nucleotide binding favors closure of the nucleotide-binding cleft of Arp3, but no large-scale conformational changes in the complex. Thus, ATP binding does not directly activate Arp2/3 complex but is part of a network of interactions that contribute to nucleation. We compared nucleotide-induced conformational changes of residues lining the cleft in Arp3 and actin structures to construct a movie depicting the proposed ATPase cycle for the actin family. Chemical crosslinking stabilized subdomain 1 of Arp2, revealing new electron density for 69 residues in this subdomain. Steric clashes with Arp3 appear to be responsible for intrinsic disorder of subdomains 1 and 2 of Arp2 in inactive Arp2/3 complex.

Publication types

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

MeSH terms

  • Actin Cytoskeleton
  • Actin-Related Protein 2-3 Complex / chemistry*
  • Actin-Related Protein 2-3 Complex / metabolism*
  • Actins / chemistry*
  • Actins / metabolism*
  • Adenosine Diphosphate / chemistry
  • Adenosine Diphosphate / metabolism
  • Adenosine Triphosphatases / metabolism
  • Adenosine Triphosphate / chemistry
  • Adenosine Triphosphate / metabolism
  • Animals
  • Binding Sites
  • Cattle
  • Cross-Linking Reagents / chemistry
  • Glutaral / chemistry
  • Humans
  • Kinetics
  • Macromolecular Substances / chemistry*
  • Macromolecular Substances / metabolism
  • Models, Molecular
  • Nucleotides / chemistry
  • Nucleotides / metabolism*
  • Protein Conformation
  • Protein Interaction Mapping*
  • Protein Structure, Tertiary


  • Actin-Related Protein 2-3 Complex
  • Actins
  • Cross-Linking Reagents
  • Macromolecular Substances
  • Nucleotides
  • Adenosine Diphosphate
  • Adenosine Triphosphate
  • Adenosine Triphosphatases
  • Glutaral