The 3D structure of the actin filament branch junction at 2.5 nm resolution from electron tomography confirmed that Arp2 is located next to Arp3 in the branch junction, consistent with the Arps forming a short-pitch actin filament helix (5). Our PPG collaborators fit the inactive crystal structure into the tomographic density by a rigid body movement of Arp2 next to Arp3. Since one can isolate Arp2/3 complex lacking Arp2 (S2), it is conceivable that Arp2 moves in this way, tethered to the rest of the complex by the Nterminus of ARPC5. However, we also found that fission yeast survive deletion of the N-terminus of ARPC5 with normal appearing actin patches (Nolen and Pollard, unpublished observations). Therefore, we must consider other mechanisms to move Arp2 next to Arp3, such as maintaining the contacts of Arp2 with ARPC1, ARPC2 and ARPC4 while bending ARPC2/and ARPC4 (and other subunits) to bring Arp2 next to Arp3. Rationale: We feel that crystallization of the entire branch junction is unlikely, but molecular dynamics simulations offer an alternative experimental approach to explore the conformation change that occurs within Arp2/3 complex during the transition from the inactive state to the branch junction.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Program Projects (P01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-CB-D)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Yale University
New Haven
United States
Zip Code
Anderson, Karen L; Page, Christopher; Swift, Mark F et al. (2017) Nano-scale actin-network characterization of fibroblast cells lacking functional Arp2/3 complex. J Struct Biol 197:312-321
Wang, Pei-Shan; Chou, Fu-Sheng; Ramachandran, Sreekumar et al. (2016) Crucial roles of the Arp2/3 complex during mammalian corticogenesis. Development 143:2741-52
Pollard, Thomas D (2016) Actin and Actin-Binding Proteins. Cold Spring Harb Perspect Biol 8:
Page, Christopher; Hanein, Dorit; Volkmann, Niels (2015) Accurate membrane tracing in three-dimensional reconstructions from electron cryotomography data. Ultramicroscopy 155:20-26
Jurgenson, Christopher T; Pollard, Thomas D (2015) Crystals of the Arp2/3 complex in two new space groups with structural information about actin-related protein 2 and potential WASP binding sites. Acta Crystallogr F Struct Biol Commun 71:1161-8
Li, Yongchao; Wang, Pei-Shan; Lucas, George et al. (2015) ARP2/3 complex is required for directional migration of neural stem cell-derived oligodendrocyte precursors in electric fields. Stem Cell Res Ther 6:41
Tee, Yee Han; Shemesh, Tom; Thiagarajan, Visalatchi et al. (2015) Cellular chirality arising from the self-organization of the actin cytoskeleton. Nat Cell Biol 17:445-57
Suraneni, Praveen; Fogelson, Ben; Rubinstein, Boris et al. (2015) A mechanism of leading-edge protrusion in the absence of Arp2/3 complex. Mol Biol Cell 26:901-12
Volkmann, Niels (2014) The joys and perils of flexible fitting. Adv Exp Med Biol 805:137-55
Volkmann, Niels; Page, Christopher; Li, Rong et al. (2014) Three-dimensional reconstructions of actin filaments capped by Arp2/3 complex. Eur J Cell Biol 93:179-83

Showing the most recent 10 out of 55 publications