Fig. 5.

Variable resolvability of tubulin in a CF segment of cryo-EM density by subtomogram averaging from detergent-extracted parasite. (A) CFs are unusual tubulin-based fibrils. Each fibril contains nine columns of tubulin (blue and cyan), associated with CF-associated densities within the concave inner face of the CF (yellow) and on the outer convex face (magenta, green, orange). This is shown axially from various views rotated around the long axis. (B) Zoomed-in cryo-EM density of two tubulin components in each of columns 1 to 9. Tubulin columns were fitted to the conoid average densities. A total of nine columns were segmented, shown axially with alternating light and dark blue colors (top) from various views. (C) Nontubulin groove densities appear every 80 Å, shown between columns 3 and 4 (magenta), on the outside of columns 5 to 8 (orange and brown), and between columns 8 and 9 (green). The plus (+) and minus (−) ends of the microtubule are as indicated in A and the first column of B.