Figure 6.

Distribution and structure of MIPs in DRG axons. (A) Distribution of MIP densities in DRG MTs (72.0 ± 10.6, n = 147). For each MT, the number of MIPs was divided by the MT length to give MIPs per micrometer. (B) Tomogram slice and cartoon showing connections (white arrowheads) between MIPs and the MT wall. (C) Cartoon of MT lattice break exemplifying the measurement of MIP density within (light green) or adjacent to (dark green) lattice break. Arrowheads show boundary of the break. (D) Comparison of expected (Exp.) and observed (Obs.) MIP density at sites of MT breaks and ends. The expected density calculated in A is given for each MT (69 ± 9, n = 6 for MTs with breaks, 76 ± 11, n = 9 for MTs with ends). The observed density was calculated within breaks (78 ± 27, n = 6), adjacent to breaks (89 ± 14, n = 6), or adjacent to ends (86 ± 16, n = 9). The MIP densities adjacent to breaks are the average counted either side of the break. ns, P = 0.3022 for within break; **, P = 0.0033 for adjacent to break; ns, P = 0.1025 for adjacent to end; paired two-tailed t test. Error bars show mean and SD. (E) Low-resolution subtomogram average of MIPs viewed from the front and back. (F) Tomogram slice showing MT and refined particle positions of MIPs after subtomogram averaging. (G) Size comparison of an MT (white, luminal side view), MIP (blue), α/β-tubulin dimer (PDB accession no. 6RZB, orange), β-actin (PDB accession no. 2HF3, light orange), and a-TAT1 (PDB accession no. 4GS4, yellow).