A pinwheel-shaped structure consisting of a tetrameric NEDD1 helical bundle and four MZT1:GCP3-NHD modules docks onto the base of the asymmetric cone-shaped human γ-TuRC. (A) Schematic of the human NEDD1 sequence. A zoom in on the C-terminal helical region predicted to form several α-helices is shown. Secondary structure predictions are taken from UniProt Consortium (2023). (B) Cartoon representation of the MZT1:GCP3-NHD structure in the γ-TuRC lumenal bridge, from PDB ID: 6X0U (Wieczorek et al., 2020a). (C) Two views of an AlphaFold prediction containing four copies each of NEDD1 residues 571–660, MZT1, and GCP3 residues 1–120. The model on the left is colored according to the predicted local distance difference test (pLDDT) score from the AlphaFold prediction. (D) Two views of the consensus rec-γ-TuRC density map (surface representation). The seam, lumenal bridge, and pinwheel-shaped densities are labeled; the pinwheel-shaped density is colored in lavender. Map resolution is 4.7 Å, but is shown at a low threshold to include features with weaker density. Higher resolution features can be found in Fig. S3 B. (E) Two views of the pinwheel density postprocessed using EMready (He et al., 2023) (light pink surface representation). The CryoSPARC postprocessed map is shown at the same threshold as in D as a transparent white surface for reference. The pinwheel axle containing the fishtail and α-helical tetramer, as well as pinwheel blades A–D, are indicated. (F) Two views of the refined γ-TuRC model in the rec-γ-TuRC consensus map, focusing on the pinwheel density. Blades C and D are omitted for clarity, and pinwheel features are labeled as in E.