Inhibition of tubulin polymerization -at a mitosis-inhibiting dose, colchicine functions by binding specifically and irreversibly to tubulin. the colchicine-tubulin complex is added at the positive end of the kinetochore, but it inhibits further addition of tubulin. the result is a biochemical capping of the tubulin at the growth end, preventing further tubulin addition. cells are blocked in metaphase and cannot escape because microtubule motors are unable to function in generating the forces required for anaphase. at higher doses of colchicine, cytosolic microtubules depolymerize. actin and myosin are involved in cytokinesis (the division of cytoplasm), whereas tubulin and the microtubules regulate separation of the daughter nuclei and their contents. taxol, like colchicine, inhibits mitosis, but it uses a different mechanism. taxol binds and stabilizes microtubules, causing a disruption of microtubule dynamics and inhibition of mitosis. taxol and colchicine are similar in binding only to alpha ,beta -tubulin-dimers and microtubules.
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