Coronin Enhances Actin Filament Severing by Recruiting Cofilin to Filament Sides and Altering F-Actin Conformation.

High rates of actin filament turnover are essential for many biological processes and require the activities of multiple actin-binding proteins working in concert. The mechanistic role of the actin filament severing protein cofilin is now firmly established; however, the contributions of other conserved disassembly-promoting factors including coronin have remained more ...
obscure. Here, we have investigated the mechanism by which yeast coronin (Crn1) enhances F-actin turnover. Using multi-color total internal reflection fluorescence microscopy, we show that Crn1 enhances Cof1-mediated severing by accelerating Cof1 binding to actin filament sides. Further, using biochemical assays to interrogate F-actin conformation, we show that Crn1 alters longitudinal and lateral actin-actin contacts and restricts opening of the nucleotide-binding cleft in actin subunits. Moreover, Crn1 and Cof1 show opposite structural effects on F-actin yet synergize in promoting release of phalloidin from filaments, suggesting that Crn1/Cof1 co-decoration may increase local discontinuities in filament topology to enhance severing.
Mesh Terms:
Actin Cytoskeleton, Actins, Binding Sites, Cofilin 1, Microfilament Proteins, Models, Molecular, Protein Binding, Protein Conformation, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
J. Mol. Biol.
Date: Sep. 25, 2015
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