title: Identification of an ATP-controlled allosteric switch that controls actin filament nucleation by Arp2/3 complex.
abstract: Nucleation of branched actin filaments by Arp2/3 complex is tightly regulated to control actin assembly in cells. Arp2/3 complex activation involves conformational changes brought about by ATP, Nucleation Promoting Factor (NPF) proteins, actin filaments and NPF-recruited actin monomers. To understand how these factors promote activation, we must first understand how the complex is held inactive in their absence. Here we demonstrate that the Arp3 C-terminal tail is a structural switch that prevents Arp2/3 complex from adopting an active conformation. The interaction between the tail and a hydrophobic groove in Arp3 blocks movement of Arp2 and Arp3 into an activated filament-like (short pitch) conformation. Our data indicate ATP binding destabilizes this interaction via an allosteric link between the Arp3 nucleotide cleft and the hydrophobic groove, thereby promoting the short-pitch conformation. Our results help explain how Arp2/3 complex is locked in an inactive state without activators and how autoinhibition is relieved.
authors.affiliation: Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: Max
authors.identifier: 0000-0003-1744-9675
authors.initials: M
authors.lastname: Rodnick-Smith
authors.affiliation: Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: Su-Ling
authors.initials: SL
authors.lastname: Liu
authors.affiliation: Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: Connor J
authors.initials: CJ
authors.lastname: Balzer
authors.affiliation: Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Luan
authors.affiliation: Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: Brad J
authors.initials: BJ
authors.lastname: Nolen
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051377:Actin-Related Protein 2 / Q000235:genetics / Q000378:metabolism*; D051376:Actin-Related Protein 2-3 Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051378:Actin-Related Protein 3 / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000595:Amino Acid Sequence; D017124:Conserved Sequence; D011487:Protein Conformation; D055503:Protein Multimerization; D055550:Protein Stability; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C477632:ARP2 protein, S cerevisiae; C102245:ARP3 protein, S cerevisiae; D051377:Actin-Related Protein 2; D051376:Actin-Related Protein 2-3 Complex; D051378:Actin-Related Protein 3; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D000255:Adenosine Triphosphate