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Updated: Jul 5, 2026

Aip1p Dynamics Are Altered by the R256H Mutation in Actin
Published on: July 30, 2014
X-ray scattering study of activated Arp2/3 complex with bound actin-WCA
Malgorzata Boczkowska1, Grzegorz Rebowski, Maxim V Petoukhov
1Department of Physiology, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, A507 Richards Building, Philadelphia, PA 19104-6085, USA.
Abstract:
Previous structures of Arp2/3 complex, determined in the absence of a nucleation-promoting factor and actin, reveal its inactive conformation. The study of the activated structure has been hampered by uncontrollable polymerization. We have engineered a stable activated complex consisting of Arp2/3 complex, the WCA activator region of N-WASP, and one actin monomer, and studied its structure in solution by small angle X-ray scattering (SAXS). The scattering data support a model in which the first actin subunit binds at the barbed end of Arp2, and disqualify an alternative model that places the first actin subunit at the barbed end of Arp3. This location of the first actin and bound W motif constrains the binding site of the C motif to subunits Arp2 and ARPC1, from where the A motif can reach subunits Arp3 and ARPC3. The results support a model of activation that is consistent with most of the biochemical observations.
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