Fig. 4.
Forced walk of the ring. (A) With increasing ring-tubulin affinity, the ring steps slower. The irregular features of ring forward motion are caused by the stochasticity and asynchrony in PF splitting and walking of different linkers. (B) The linkers step asynchronously (shown are the z coordinates of their MT-associated ends) and in 8-nm steps (arrows point to some), whereas the steps of the ring's center are more variable in size. (C) With increasing load, the duration of ring pauses increases, and the ring walks more slowly (kDAM 13 kBT). (D) The rate of coupler's movement with the depolymerizing MT end is a blueprint for the strength of its affinity to the MT wall and thus for the mechanism of its motion.