title: Small molecules CK-666 and CK-869 inhibit actin-related protein 2/3 complex by blocking an activating conformational change.
abstract: 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.
authors.affiliation: Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA.
authors.forename: Byron
authors.initials: B
authors.lastname: Hetrick
authors.forename: Min Suk
authors.initials: MS
authors.lastname: Han
authors.forename: Luke A
authors.initials: LA
authors.lastname: Helgeson
authors.forename: Brad J
authors.initials: BJ
authors.lastname: Nolen
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D002417:Cattle; D018360:Crystallography, X-Ray; D007211:Indoles / Q000494:pharmacology*; D008958:Models, Molecular; D016566:Organoselenium Compounds / Q000494:pharmacology*; D017646:Organosilicon Compounds / Q000494:pharmacology*; D011487:Protein Conformation / Q000187:drug effects*; D060066:Protein Interaction Maps / Q000187:drug effects
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; C543733:CK-0944666; C585054:CK-869; D007211:Indoles; D016566:Organoselenium Compounds; D017646:Organosilicon Compounds; D000255:Adenosine Triphosphate