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J Mol Biol. 2008 Feb 22;376(3):607-13. doi: 10.1016/j.jmb.2007.12.007. Epub 2007 Dec 8.

Coronin-1A stabilizes F-actin by bridging adjacent actin protomers and stapling opposite strands of the actin filament.

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Department of Biochemistry and Molecular Genetics, University of Virginia, Box 800733, Charlottesville, VA 22908-0733, USA.


Coronins are F-actin-binding proteins that are involved, in concert with Arp2/3, Aip1, and ADF/cofilin, in rearrangements of the actin cytoskeleton. An understanding of coronin function has been hampered by the absence of any structural data on its interaction with actin. Using electron microscopy and three-dimensional reconstruction, we show that coronin-1A binds to three protomers in F-actin simultaneously: it bridges subdomain 1 and subdomain 2 of two adjacent actin subunits along the same long-pitch strand, and it staples subdomain 1 and subdomain 4 of two actin protomers on different strands. Such a mode of binding explains how coronin can stabilize actin filaments in vitro. In addition, we show which residues of F-actin may participate in the interaction with coronin-1A. Human nebulin and Xin, as well as Salmonella invasion protein A, use a similar mechanism to stabilize actin filaments. We suggest that the stapling of subdomain 1 and subdomain 4 of two actin protomers on different strands is a common mechanism for F-actin stabilization utilized by many actin-binding proteins that have no homology.

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