7TPT

Single-particle Cryo-EM structure of Arp2/3 complex at branched-actin junction.

Summary for 7TPT

• Entry DOI: 10.2210/pdb7tpt/pdb
• EMDB information: 26063
• Related PRD ID: PRD_002366
• Descriptor: Actin-related protein 3, MAGNESIUM ION, ADENOSINE-5'-DIPHOSPHATE, ... (11 entities in total)
• Functional Keywords: arp2/3, actin, cytoskeletal protein, actin regulator, structural protein
• Biological source: Bos taurus (cattle); More
• Total number of polymer chains: 36
• Total formula weight: 833097.77

Authors

Ding, B.,Narvaez-Ortiz, H.Y.,Nolen, B.J.,Chowdhury, S. (deposition date: 2022-01-26, release date: 2022-05-25, Last modification date: 2022-06-08)

Primary citation

Ding, B.,Narvaez-Ortiz, H.Y.,Singh, Y.,Hocky, G.M.,Chowdhury, S.,Nolen, B.J.
Structure of Arp2/3 complex at a branched actin filament junction resolved by single-particle cryo-electron microscopy.
Proc.Natl.Acad.Sci.USA, 119:e2202723119-e2202723119, 2022

PubMed Abstract: Arp2/3 complex nucleates branched actin filaments that provide pushing forces to drive cellular processes such as lamellipodial protrusion and endocytosis. Arp2/3 complex is intrinsically inactive, and multiple classes of nucleation promoting factors (NPFs) stimulate its nucleation activity. When activated by WASP family NPFs, the complex must bind to the side of a preexisting (mother) filament of actin to complete the nucleation process, ensuring that WASP-mediated activation creates branched rather than linear actin filaments. How actin filaments contribute to activation is currently not understood, largely due to the lack of high-resolution structures of activated Arp2/3 complex bound to the side of a filament. Here, we present the 3.9-Å cryo-electron microscopy structure of the Arp2/3 complex at a branch junction. The structure reveals contacts between Arp2/3 complex and the side of the mother actin filament that likely stimulate subunit flattening, a conformational change that allows the actin-related protein subunits in the complex (Arp2 and Arp3) to mimic filamentous actin subunits. In contrast, limited contact between the bottom half of the complex and the mother filament suggests that clamp twisting, a second major conformational change observed in the active state, is not stimulated by actin filaments, potentially explaining why actin filaments are required but insufficient to trigger nucleation during WASP-mediated activation. Along with biochemical and live-cell imaging data and molecular dynamics simulations, the structure reveals features critical for the interaction of Arp2/3 complex with actin filaments and regulated assembly of branched actin filament networks in cells.

PubMed: 35622886
DOI: 10.1073/pnas.2202723119

Experimental method

ELECTRON MICROSCOPY (3.9 Å)