Interaction of Tubulin and Cellular Microtubules with the New Antitumor Drug MDL 27048

mM MgClZ, 0.1 mM GTP buffer, pH 6.7, at 25 "C). Podophyllotoxin displaced the binding of MDL 27048, suggesting an overlap with the colchicine-bind- ing site. Assembly of purified tubulin into microtubules was inhibited by substoichiometric concentrations of MDL 27048, which also induced