3M3N

Structure of a Longitudinal Actin Dimer Assembled by Tandem W Domains

Summary for 3M3N

• Entry DOI: 10.2210/pdb3m3n/pdb
• Related: 3M1F
• Descriptor: Actin, alpha skeletal muscle, Neural Wiskott-Aldrich syndrome protein, ADENOSINE-5'-TRIPHOSPHATE, ... (4 entities in total)
• Functional Keywords: actin dimer, atp-binding, actin cytoskeleton, methylation, muscle protein, actin-binding, motor protein, structural protein
• Biological source: Mus musculus (mouse); More
• Cellular location: Cytoplasm, cytoskeleton: P68135 P20065
• Total number of polymer chains: 3
• Total formula weight: 95940.22

Authors

Rebowski, G.,Namgoong, S.,Dominguez, R. (deposition date: 2010-03-09, release date: 2010-07-28, Last modification date: 2023-09-06)

Primary citation

Rebowski, G.,Namgoong, S.,Boczkowska, M.,Leavis, P.C.,Navaza, J.,Dominguez, R.
Structure of a longitudinal actin dimer assembled by tandem w domains: implications for actin filament nucleation.
J.Mol.Biol., 403:11-23, 2010

PubMed Abstract: Actin filament nucleators initiate polymerization in cells in a regulated manner. A common architecture among these molecules consists of tandem WASP homology 2 domains (W domains) that recruit three to four actin subunits to form a polymerization nucleus. We describe a low-resolution crystal structure of an actin dimer assembled by tandem W domains, where the first W domain is cross-linked to Cys374 of the actin subunit bound to it, whereas the last W domain is followed by the C-terminal pointed end-capping helix of thymosin β4. While the arrangement of actin subunits in the dimer resembles that of a long-pitch helix of the actin filament, important differences are observed. These differences result from steric hindrance of the W domain with intersubunit contacts in the actin filament. We also determined the structure of the first W domain of Vibrio parahaemolyticus VopL cross-linked to actin Cys374 and show it to be nearly identical with non-cross-linked W-Actin structures. This result validates the use of cross-linking as a tool for the study of actin nucleation complexes, whose natural tendency to polymerize interferes with most structural methods. Combined with a biochemical analysis of nucleation, the structures may explain why nucleators based on tandem W domains with short inter-W linkers have relatively weak activity, cannot stay bound to filaments after nucleation, and are unlikely to influence filament elongation. The findings may also explain why nucleation-promoting factors of the Arp2/3 complex, which are related to tandem-W-domain nucleators, are ejected from branch junctions after nucleation. We finally show that the simple addition of the C-terminal pointed end-capping helix of thymosin β4 to tandem W domains can change their activity from actin filament nucleation to monomer sequestration.

PubMed: 20804767
DOI: 10.1016/j.jmb.2010.08.040

Experimental method

X-RAY DIFFRACTION (7 Å)