Molecule of the Month: Actin Branching by Arp2/3 Complex
By mimicking actin, Arp2/3 complex helps build a complex cytoskeleton that supports and shapes cells.
Exploring the Structure
Arp2/3 Complex at an Actin Branch
PDB entry 7tpt includes Arp2/3 complex along with short pieces of the mother and daughter actin strands. This allows us to look closely and the interactions between proteins. The interaction between Arp3 and the first actin in the daughter filament is shown here. Notice that the two proteins have a very similar shape, including a similar binding site for ATP. To explore the whole structure and the Arp2 interaction, click on the picture for an interactive JSmol.
Topics for Further Discussion
- You can compare the structures of Arp3, Arp2, and actin in more detail using the Structure Alignment Tool.
- Structures of many other proteins related to the actin cytoskeleton are available in the PDB archive. Try searching at the main RCSB site for formin, cofilin, actinin, and of course, the motor protein myosin.
Related PDB-101 Resources
- Browse Molecular Infrastructure
- 7tpt: Ding, B., Narvaez-Ortiz, H.Y., Singh, Y., Hocky, G.M., Chowdhury, S., Nolen, B.J. (2022) Structure of Arp2/3 complex at a branched actin filament junction resolved by single-particle cryo-electron microscopy. Proc Natl Acad Sci U S A 119: e2202723119-e2202723119.
- 7pdz: Funk, J., Merino, F., Schaks, M., Rottner, K., Raunser, S., Bieling, P. (2021) A barbed end interference mechanism reveals how capping protein promotes nucleation in branched actin networks. Nat Commun 12: 5329-5329.
- Merino, F., Pospich, S., Rausner, S. (2020) Towards a structural understanding of the remodeling of the actin cytoskeleton. Sem Cell Develop Biol 102, 51-64.
- Pollard, T.D. (2016) Actin and actin-binding proteins. Cold Spring Harbor Perspect Biol 8, a018226.
- 2btf: Schutt, C.E., Myslik, J.C., Rozycki, M.D., Goonesekere, N.C., Lindberg, U. (1993) The structure of crystalline profilin-beta-actin. Nature 365: 810-816.
November 2022, David Goodselldoi:10.2210/rcsb_pdb/mom_2022_11