Identification of an ATP-controlled allosteric switch that controls actin filament nucleation by Arp2/3 complex

Nat Commun. 2016 Jul 15;7:12226. doi: 10.1038/ncomms12226.

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.

Publication types

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

MeSH terms

  • Actin Cytoskeleton / metabolism*
  • Actin-Related Protein 2 / genetics
  • Actin-Related Protein 2 / metabolism*
  • Actin-Related Protein 2-3 Complex / chemistry
  • Actin-Related Protein 2-3 Complex / genetics
  • Actin-Related Protein 2-3 Complex / metabolism*
  • Actin-Related Protein 3 / genetics
  • Actin-Related Protein 3 / metabolism
  • Adenosine Triphosphate / metabolism*
  • Amino Acid Sequence
  • Conserved Sequence
  • Protein Conformation
  • Protein Multimerization
  • Protein Stability
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Schizosaccharomyces / genetics
  • Schizosaccharomyces / metabolism
  • Schizosaccharomyces pombe Proteins / genetics
  • Schizosaccharomyces pombe Proteins / metabolism*

Substances

  • ARP2 protein, S cerevisiae
  • ARP3 protein, S cerevisiae
  • Actin-Related Protein 2
  • Actin-Related Protein 2-3 Complex
  • Actin-Related Protein 3
  • Saccharomyces cerevisiae Proteins
  • Schizosaccharomyces pombe Proteins
  • Adenosine Triphosphate