The action of cytochalasin A on the in vitro polymerization of brain tubulin and muscle G-actin.

The presence of cytochalasin A inhibits the self-assembly of beef brain tubulin and rabbit muscle G-actin in vitro and also decreases the colchicine binding of tubulin. Prior reaction of cytochalasin A with 2-mercaptoethanol destroys its inhibitory effects. It is shown that cytochalasin A exerts its actions by reacting with sulfhydryl groups, possibly causing irreversible structural changes in the proteins. Cytochalasin B does not affect the tubulin assembly reaction.