Figure 2.

Taccalonolide A is unable to form cold stable microtubules in cell lysates. HeLa cell lysates were collected, chilled to depolymerize microtubules and then treated with 20 µM paclitaxel or 20 µM taccalonolide A for 5 min at 37°C to reform microtubules. Lysates were then re-chilled to evaluate the ability of the stabilizers to initiate the formation of cold-stable microtubules. Microtubule polymer was pelleted by centrifugation and soluble tubulin heterodimers remained in the supernatant. The total protein (A) and β-tubulin (B) levels present in the supernatant (S), wash (W) and pellet (P) fractions were evaluated by total protein staining or β-tubulin immunoblotting, respectively. The location of tubulin in the total protein stained gel is indicated with an arrow.