+ end of assembled microtubules + end of axonemal microtubules Axoneme
cool to 4'C Tubulin cmers Warm to 37'C
50 Catastrophe 40 Disassembly c30 20 Rescue ≌10 Assembly 0 60 90 Time(min) A FIGURE 19-13 Dynamic instability of microtubules in vitro. Individual microtubules can be observed in the light micro
nucleating sites (rings of ?tubulin) pair of MTOC (B) microtubules growing from ating site
CHaO NH一C-CH3 CH3O CHao CH3 H3C-C-0 o HaC c-NH一CH-CH-c-0 OH o-C-CH C-0 A FIGURE 19-16 Structures of colchicine and taxol. These and other drugs that interfere with normal assembly and disassembly of microtubules have an antimitotic effect that is particularly devastating to rapidly dividing cells, such as cancer cells