Twinfilin Family of Actin Monomer-Binding Proteins

Twinfilin family actin monomer-binding proteins are conserved in evolution from yeasts to mammals. They bind ADP-actin monomers with high affinity and prevent the assembly of actin monomers into filament ends. In addition to monomeric actin, twinfilins also bind and cap actin filament barbed ends, and interact direcdy with heterodimeric capping proteins. Interaction with capping protein is necessary for twinfilins localization to the cortical actin cytoskeleton at least in budding yeast. Genetic studies on yeast and Drosophila demonstrate that twinfilin is intimately involved in the regulation of actin dynamics in cells, and that the lack of twinfilin results in uncontrolled actin filament assembly. Together, these data suggest that twinfilins play an important role in actin dynamics by preventing unwanted actin filament assembly in cells. However, the exact mechanism by which twinfilin regulates actin filament turnover and contributes to actin-dependent cellular processes remains to be elucidated.