Ansamitocin P-3 is a microtubule inhibitor. Ansamitocin P-3 is a macrocyclic antitumor antibiotic.

Microtubule^[1]

Ansamitocin P3 potently inhibits the proliferation of MCF-7, HeLa, EMT-6/AR1 and MDA-MB-231 cells in culture with a half-maximal inhibitory concentration of 20±3, 50±0.5, 140±17, and 150±1.1 pM, respectively. Further, Ansamitocin P3 is found to bind to purified tubulin in vitro with a dissociation constant (K_d) of 1.3±0.7 µM. The binding of Ansamitocin P3 induces conformational changes in tubulin. Ansamitocin P3 inhibits the proliferation of MCF-7, HeLa, EMT-6/AR1 and MDA-MB-231 cells in culture in a concentration dependent manner. Flow cytometric analysis of PI-stained cells suggests that Ansamitocin P3 inhibits the cell cycle progression of MCF-7 cells in G2/M phase. For example, 26, 50 and 70% of the cells are found to be in G2/M phase in the absence and presence of 50 and 100 pM Ansamitocin P3, respectively^[2].

• [1]. Kiso T, et al. Screening for microtubule-disrupting antifungal agents by using a mitotic-arrest mutant of Aspergillus nidulans and novel action of phenylalanine derivatives accompanying tubulin loss. Antimicrob Agents Chemother. 2004 May;48(5):1739-48.

  [2]. Venghateri JB, et al. Ansamitocin P3 depolymerizes microtubules and induces apoptosis by binding to tubulin at thevinblastine site. PLoS One. 2013 Oct 4;8(10):e75182.