INTERACTION OF CRYPTOPHYCIN-1 WITH TUBULIN AND MICROTUBULES

The cryptophycins are newly discovered antimitotic agents isolated fro m the cyanobacterium Nostoc, Previous studies using cultured cells dem onstrated that microtubules are the target of these compounds, We have studied the interaction of cryptophycin 1 with tubulin and microtubul es in vitro, Cryptophycin 1 is an effective inhibitor of tubulin polym erization, causes tubulin to aggregate, and depolymerizes microtubules to linear polymers somewhat similar to the spiral-like structures pro duced by the Vinca alkaloids, Cryptophycin 1 also inhibits vinblastine binding to tubulin but not colchicine binding, Thus, it appears that the cryptophycins may bind to the Vinca site in tubulin or to a site t hat overlaps with the Vinca site.