In vitro assembly of rat pancreas tubulin in the presence of taxol.

A rat pancreas supernatant was applied to an affinity column where colchicine analogues had been coupled to CNBr-Sepharose 4B, and subsequent elution with 0.35 M sodium chloride gave tubulin among other proteins. Incubation with 5 microM taxol, a natural plant product, resulted in the assembly of tubulin as checked by turbidimetry at 350 nm. Electron microscope observation of the structures obtained revealed (i) the presence of numerous microtubules with the same morphological parameters as brain microtubules, and (ii) that immunoreactive tubulin molecules were well-distributed along the microtubules as shown by the immunogold staining technique. Biochemical evidence indicated that the microtubules obtained were exclusively composed of tubulin, as demonstrated by slab gel polyacrylamide electrophoresis and by immunoblot staining with highly specific tubulin antibodies.