AI Article Synopsis
- The Spire protein effectively regulates actin assembly through unique structural complexes with actin, which were analyzed using various advanced microscopy and scattering techniques.
- Spire-actin complexes feature a distinctive shape where WH2 domains align actins, promoting efficient nucleation for polymerization but potentially disrupting existing filaments under specific conditions.
- This study suggests that the molecular mechanisms identified for Spire could also relate to other proteins with similar WH2 domain configurations in their actin interactions.
Article Abstract
The Spire protein is a multifunctional regulator of actin assembly. We studied the structures and properties of Spire-actin complexes by X-ray scattering, X-ray crystallography, total internal reflection fluorescence microscopy, and actin polymerization assays. We show that Spire-actin complexes in solution assume a unique, longitudinal-like shape, in which Wiskott-Aldrich syndrome protein homology 2 domains (WH2), in an extended configuration, line up actins along the long axis of the core of the Spire-actin particle. In the complex, the kinase noncatalytic C-lobe domain is positioned at the side of the first N-terminal Spire-actin module. In addition, we find that preformed, isolated Spire-actin complexes are very efficient nucleators of polymerization and afterward dissociate from the growing filament. However, under certain conditions, all Spire constructs--even a single WH2 repeat--sequester actin and disrupt existing filaments. This molecular and structural mechanism of actin polymerization by Spire should apply to other actin-binding proteins that contain WH2 domains in tandem.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3241762 | PMC |
| http://dx.doi.org/10.1073/pnas.1115465108 | DOI Listing |
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