Molecular architecture of the Spire-actin nucleus and its implication for actin filament assembly

Sitar, T., Gallinger, J., Ducka, A. M., Ikonen, T. P., Wohlhoefler, M., Schmoller, K. M., Bausch, A. R., Joel, P., Trybus, K. M., Noegel, A. A., Schleicher, M., Huber, Robert and Holak, T. A. 2011. Molecular architecture of the Spire-actin nucleus and its implication for actin filament assembly. Proceedings of the National Academy of Sciences 108 (49) , pp. 19575-19580. 10.1073/pnas.1115465108

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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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Biosciences
Subjects:	Q Science > Q Science (General)
Uncontrolled Keywords:	cytoskeleton; nucleation
Publisher:	National Academy of Sciences
ISSN:	0027-8424
Last Modified:	24 Jun 2017 09:33
URI:	https://orca.cardiff.ac.uk/id/eprint/32209

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