Promiscuous interactions of human septins: The GTP binding domain of SEPT7 forms filaments within the crystal

► We describe the heterologous expression of the GTP-binding domain of septin 7. ► Crystals of the purified protein were obtained. ► The GTP-binding domains form filaments within the crystal lattice. ► These employ identical interfaces to those described for the hetero-filament of septins 2, 6 and 7. ► We discuss the implications for filament assembly.