Abstract
Cofilin, one of actin-binding proteins, promotes depolymerization and severing of actin filament. The filament disassembly is essential for turnover of actin cytoskeleton. In addition, it is also reported that cofilin binding alters torsional structure of actin filament. It is reasonable to think that the change of molecular behavior of actin filament induced by cofilin binding is associated with promotion of filament disassembly. Therefore we analyzed the relationship between them by use of molecular dynamics simulation. We performed equilibration simulation of cofilin-free and cofilin-decorated actin filament. For the purpose of discussing the relationship between torsional behavior and disassembly of actin filament, we calculated local twist angle of actin filament and interaction energy between adjacent actin subunits. The interaction energy indicates the extent of filament disassembly. From the simulation results, twist-dependent energy landscapes between adjacent subunits were observed in both cofilin-free and cofilin-decorated actin filament. High energy states near one specific twist angle are observed only in cofilin-decorated actin filament, which shows the disassembly of actin filament caused by cofilin binding. Additionally, another energy landscape was observed between cofilin and actin in cofilin-decorated actin filament, which accounts for the high energy states between adjacent actin subunits.
