Microtubule fragments exhibiting net treadmilling in a Rac1(Q61L)-expressing PtK1 cell. Microtubule plus ends undergo dynamic instability while their minus ends depolymerize, resulting in net treadmilling of the microtubule lattice. Images were taken every 5 s and are played back at 15 frames/s. For still images, see Fig. 2 D.
