Figure 5.

Structure and assembly of SAS-6. (a) Domain organization and ribbon diagram representation of SAS-6. SAS-6 molecules form a parallel dimer via their coiled-coil domains. The SAS-5 binding site is indicated. (b) Assembly of nine SAS-6 dimers into a cartwheel-like structure via intermolecular interactions of the head domains around the ring. (c) Coloured schematic showing the head–head interaction between two neighbouring SAS-6 dimers. (d) Ribbon diagram of the crystal structure of the C. elegans SAS-6 head domain dimer (PDB code: 3PYI). Arrows point to the loops mediating the intermolecular interaction. (e) Three working models for formation of the cylinder-like structure by SAS-6. The spokes formed by SAS-6 coiled-coils are omitted for clarity.