Ansamitocin P-3 is a microtubule depolymerizing agent that can be isolated from culture broths of certain Gram-positive bacteria. It binds tubulin (Kd = 1.3 μM), depolymerizes microtubules in both interphase and mitosis, and perturbs chromosome segregation. Ansamitocin P-3 also activates the spindle checkpoint surveillance proteins Mad2 and BubR1, blocking cell cycling during mitosis. It inhibits the growth of cancer cells in culture and significantly suppresses the growth of several cancer tumors in mice, prolonging survival time.
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