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Arp2/3 complex from Acanthamoeba binds profilin and cross-links actin filaments
R D Mullins1, J F Kelleher, J Xu
1The Salk Institute for Biological Studies, La Jolla California 92037, USA.
Molecular Biology of the Cell
|May 16, 1998
Summary
The Arp2/3 complex interacts with profilin via its Arp2 subunit, influencing actin filament structure. This complex cross-links actin filaments, affecting cell motility and leading edge dynamics.
Area of Science:
- Cell Biology
- Biochemistry
- Biophysics
Background:
- The Arp2/3 complex is crucial for actin cytoskeleton organization.
- Its interaction with profilin, a known actin-binding protein, was previously poorly understood.
Purpose of the Study:
- To elucidate the mechanism of Arp2/3 complex interaction with profilin.
- To investigate the structural and functional consequences of this interaction.
Main Methods:
- Chemical cross-linking to identify interacting subunits.
- Analytical ultracentrifugation to determine binding affinity.
- Actin filament cross-linking assays.
- Immunofluorescence microscopy for protein localization.
Main Results:
- The Arp2 subunit directly binds profilin at its actin-binding site.
- Profilin binds the Arp2/3 complex with intermediate affinity (Kd = 7 μM).
- Arp2/3 complex cross-links actin filaments into stiffer networks.
- Arp2/3 complex localizes to the leading edge of motile Acanthamoeba.
Conclusions:
- Arp2/3 complex plays a key role in regulating actin network structure at the cell's leading edge.
- The interaction with profilin likely modulates Arp2/3 complex function in actin dynamics.
- Arp2/3 complex's ability to nucleate and cross-link actin filaments is vital for cell motility.
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