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Gelsolin is an actin-polymerization-regulating protein that has been isolated from many types of cells.1,2 Gelsolin affects actin polymerization in different ways. Gelsolin can fragment actin filaments. Gelsolin binds to the barbed ends of the fragmented actin filaments. The pointed ends of actin filaments remain free for depolymerization and polymerization. Gelsolin nucleates actin filaments to polymerize towards the pointed ends. Furthermore, gelsolin forms complexes with one or two actin molecules. These gelsolin-actin complexes lose the ability to fragment actin filaments. They cap actin filaments by binding to the barbed ends to inhibit polymerization and depolymerization of these ends (Fig. 1).1–4 These interactions of gelsolin with actin filaments are mainly regulated by the second messengers calcium and phosphatidyl inositol phosphates.1–5 Because of the versatility of regulation and interactions with actin and because of its ubiquity in eukaryotic cells gelsolin has attracted our interest. We investigated the equilibrium and the rates of various interactions of gelsolin with actin filaments.
KeywordsActin Filament Polymeric Actin Phosphatidyl Inositol Monomeric Actin Nucleation Activity
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