Lack of inhibition of carrot colchicine binding activity by podophyllotoxin

The binding of [3H]colchicine to carrot cell extract was not inhibited by an excess amount of podophyllotoxin. Under the same experimental condition, porcine brain tubulin almost completely lost its [3H]colchicine binding activity. The components in the carrot cell extract did not affect the interaction of brain tubulin and podophyllotoxin.