Interaction of arenastatin A with porcine brain tubulin

Arenastatin A, isolated from the Okinawan marine sponge Dysidea arenaria, is an antimitotic depsipeptide containing a 16-membered ring. Interaction of the compound with tubulin was investigated by the use of [3H]arenastatin A and other microtubule disruptors. Scatchard analysis indicated the presence of one binding site for arenastatin A per tubulin heterodimer with a dissociation constant (Kd) of 1.8 x 10(-6) M. Rhizoxin was a competitive inhibitor of arenastatin A binding, and vinblastine also inhibited arenastatin A binding in a partially competitive manner. Arenastatin A had no inhibitory effect on colchicine binding to tubulin.