 Left. A surface representation (green) of an acrosomal filament isolated from the acrosomal bundle. The major features include a central column of density to which we can fit the atomic model of actin (subunits shown in red, white, and blue). Helically wound around this is the cross-linker, scruin, which binds strongly to the actin of this filament and makes other interactions with the scruin of neighboring filaments to form the crystalline bundle. |