Fig. 3: Paracrystalline network of the PFR distal zone and structural interpretation of subunits.

a An overall surface view of a PFR distal zone encompassing four SSN planes (different colors) and their connecting wires, showing the paracrystalline arrangement. The view is looking at the PFR distal zone from the axoneme. b, c Two orthogonal surface views of a at the sectional planes indicated by the dashed lines in a, showing a single scissors density with wires (tan) in a stack (blue) and joined to adjacent scissors stacks (gray), forming an SSN plane of the paracrystalline zone. d–f Three orthogonal zoom-in views of a single scissors density with wires (tan) within the paracrystalline distal zone (gray). Viewing directions in d, e, and f are the same as in a, b, and c, respectively. g Predicted secondary structures of major PFR proteins from the indicated organisms, shown according to their sequence alignment. Amino acid residue numbers of T. brucei PFR1 are indicated on the top. h–j Three orthogonal views of a single scissors density with wires (transparent tan) showing a 3 coiled-coil helix bundle (PDB: 6GAO)¹⁰³ (blue) fitted into the wires.