Extended Data Fig. 3: MIPs network in A-tubule of doublet microtubules.

a, Four cross-section views of the A tubule in the doublet microtubule are shown. The MIPs network is colored in orange. Three modes of interactions between the MIPs and the protofilaments are observed (see text). The protrusions from the filamentous core are indicated by empty red arrowheads and dashed cyan ovals, respectively. b, Six cross-section views of the overlay of the average of the 48-nm repeat of doublets of mouse sperm (orange, this study) and the 48-nm repeat of doublets of bovine trachea cilia (blue, EMD-24664)²⁶. The contour levels of the two maps are adjusted so that the densities of microtubules are matched. The microtubule seam, A9 and A10 protofilaments are labeled in all views. Note there are additional densities near A9-A10 region in the mouse sperm axoneme (black circles). We observed density striations in the B-tubule in some cross sections. c, An orthogonal view of the B-tubule striations along the helical pitch of the microtubule at a high and a low threshold, respectively. Note the striations are separated by 8 nm and they cover the intradimeric interface between the α- and β-tubulins based on the model for the bovine doublet (PDB: 7rro)²⁶.