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 cancers, 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 e xperimentally amenable aggregate of parallel microtubules from the ova ries of hemipteran insects. Within seconds of exposure to taxol, the m icrotubule aggregate began to twist upon itself. After a few minutes t his movement was complete, the drug having brought about a gross rearr angement of the microtubules, involving coiling on a massive scale. Th e final form assumed by the microtubule array was influenced by pH and by the presence of microtubule-associated proteins, salt, cations, an d both hydrolysable and non-hydrolysable nucleotides. The possible mec hanisms leading to this rapid structural change are considered.