FIGURE 4:

Cryo-ET and subtomogram average of the axonemal doublet microtubule from Tetrahymena wild-type and FAP115 KO. (A, B) Longitudinal view of the averages. Wild-type (gray) and FAP115 KO (orange) are viewed from the minus ends of the doublet. The red arrows indicate the missing density in the KO axoneme that is present in the wild type. The dashed lines indicate the cross-section direction in C and D. In C, the red elliptical circles highlight the density likely attributed to Fap115, the equivalent positions in the mutant doublet in D, where the density is missing, are indicated by a black dashed circle. (E) Overlay of two averages. The black arrows indicate the likely positions of Fap115 in the wild-type structure. They show 8 nm periodicity. (F) Both structures are at 17.3 Å, determined by the FSC at 0.143 cutoff. The dips in certain frequency in the FSC curves are due to a narrow defocus range, 2.3–3.0 µm, used during the data collection. In both wild-type and FAP115 KO averages, the longitudinal segment length is 24 nm, including one 16-nm repeat of Rib72A/B. Doublet microtubules (DMTs) were averaged based on 16-nm repeat of Rib72A/B.