Small molecules CK-666 and CK-869 inhibit actin-related protein 2/3 complex by blocking an activating conformational change

Chem Biol. 2013 May 23;20(5):701-12. doi: 10.1016/j.chembiol.2013.03.019. Epub 2013 Apr 25.


Actin-related protein 2/3 (Arp2/3) complex is a seven-subunit assembly that nucleates branched actin filaments. Small molecule inhibitors CK-666 and CK-869 bind to Arp2/3 complex and inhibit nucleation, but their modes of action are unknown. Here, we use biochemical and structural methods to determine the mechanism of each inhibitor. Our data indicate that CK-666 stabilizes the inactive state of the complex, blocking movement of the Arp2 and Arp3 subunits into the activated filament-like (short pitch) conformation, while CK-869 binds to a serendipitous pocket on Arp3 and allosterically destabilizes the short pitch Arp3-Arp2 interface. These results provide key insights into the relationship between conformation and activity in Arp2/3 complex and will be critical for interpreting the influence of the inhibitors on actin filament networks in vivo.

Publication types

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

MeSH terms

  • Actin-Related Protein 2-3 Complex / antagonists & inhibitors*
  • Actin-Related Protein 2-3 Complex / chemistry*
  • Actin-Related Protein 2-3 Complex / metabolism
  • Actins / metabolism
  • Adenosine Triphosphate / metabolism
  • Animals
  • Binding Sites / drug effects
  • Cattle
  • Crystallography, X-Ray
  • Indoles / pharmacology*
  • Models, Molecular
  • Organoselenium Compounds / pharmacology*
  • Organosilicon Compounds / pharmacology*
  • Protein Conformation / drug effects*
  • Protein Interaction Maps / drug effects


  • Actin-Related Protein 2-3 Complex
  • Actins
  • CK-0944666
  • CK-869
  • Indoles
  • Organoselenium Compounds
  • Organosilicon Compounds
  • Adenosine Triphosphate