Taxol causes rapid gross structural rearrangement of a native microtubule bundle.

Taxol is an anti-mitotic agent now being used in the treatment of some cancer, although the manner of its interaction with the microtubular components of the cytoskeleton is still not fully characterized. Here we report the effects of taxol upon a huge, naturally occurring and experimentally amenable aggregate of parallel microtubules from the ovaries of hemipteran insects. Within seconds of exposure to taxol, the microtubule aggregate began to twist upon itself. After a few minutes this movement was complete, the drug having brought about a gross rearrangement of the microtubules, involving coiling on a massive scale. The final form assumed by the microtubule array was influenced by pH and by the presence of microtubule-associated proteins, salt, cations, and both hydrolysable and non-hydrolysable nucleotides. The possible mechanisms leading to this rapid structural change are considered.