Molecular mechanism of Arp2/3 complex activation by nucleation-promoting factors and an actin monomer

• 成果类型: Article
• 署名作者: Iyer, Sahithya Sridharan; Wu, Jiangbo; Pollard, Thomas D.; Voth, Gregory A.
• 署名单位: Yale University; Yale University; Yale University; University of California System; University of California Berkeley
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-10152
• DOI: 10.1073/pnas.2421467122
• 发表日期: 2025-03-11
• 关键词: syndrome protein wasp; conformational-changes; wasp/scar proteins; binding-sites; DYNAMICS; simulations; filaments; networks; signals

摘要

Arp (actin-related protein) 2/3 complex nucleates actin filament branches on the sides of preexisting actin filaments during cell and organelle movements. We used computer simulations of mammalian Arp2/3 complex to address fundamental questions about the mechanism. Metadynamics and umbrella free energy sampling simulations of the pathway revealed that a clash between the D-loop of Arp2 and Arp3 produces an energy barrier of 20 +/- 6 kcal/mol between the inactive splayed and active short-pitch conformations of Arp2/3 complex. Atomistic molecular dynamics simulations showed that binding the CA motif of the nucleation-promoting factor Neuronal Wiskott-Aldrich Syndrome Protein (N-WASp) to inactive, splayed Arp2/3 complex shifts it toward the short-pitch active conformation and opens a binding site for an actin monomer on Arp3. Other simulations showed that this actin monomer stabilizes a transition state of Arp2/3 complex. These observations together with prior experimental work provide insights required to propose a physically grounded pathway for actin filament branch formation.