Interaction of the novel agent amphethinile with tubulin

The novel agent amphethinile is shown to inhibit tubulin assembly in vitro. This agent is capable of displacing colchicine but not vinblastine from tubulin and causes a stimulation in GTPase activity in vitro. The affinity constant for the association of this drug with tubulin has been determined (Ka = 1.3 x 10(6) M-1). It is concluded that amphethinile belongs to the class of agents which share a common binding site with colchicine on the tubulin molecule.