Figure 3.

Enrichment of luminal particles at depolymerizing microtubule ends and modes of binding to the microtubule wall. (A) A slice through a tomogram, corrected for the CTF (left), and a surface-rendered representation (right), showing the end of a shrinking neuronal process with depolymerizing microtubules. The depolymerizing state of the microtubules is indicated by the flared ends of the protofilaments, which are shown in different tomographic sections in the insets (the left and right microtubule flares are displayed in the bottom and top insets, respectively). The color coding is as in Fig. 2, with the plasma membrane depicted in blue. The arrowheads indicate the flared protofilaments. Bar, 50 nm. (B) Examples of luminal particles used for averaging. Most of the particles have apparent connections to the microtubule wall. (C) Surface-rendered averaged volumes in top views (top row) and side views (bottom row). Two types of interactions with the tubulin wall could be detected; single contact (left) and double contact (middle); some particles had no detectable contact (right). All individual panels in B and C are 35 nm wide.