Structures of septin filaments prepared from rat brain and expressed in bacteria

► Septin in lipid raft was further purified. ► Circular bundles of filaments with a diameter of ∼0.4 μm were observed. ► Septin expressed in bacteria showed circular bundles with a diameter of ∼0.6 μm. ► The curvature of septin filaments may be regulated by the regulatory factor(s).