The assembly of tubulin (7 μM) was assessed in polymerization buffer (50 mM 2-(N-morpholino) ethanesulfonic acid buffer pH 6.6 containing 100 mM KCl, 1 mM DTE, 1 mM MgCl2 and 1 mM ethylene glycol tetraacetic acid) at 37 °C. The tubulin polymerization into MTs was induced by the addition of 3 μM of the different TPPP/p25 forms. In another set of experiments, the polymerization of 10 μM tubulin into MTs was induced by the addition of 20 μM paclitaxel then subsequently 3 μM TPPP/p25 proteins were added to the solution. The optical density was monitored at 350 nm by a Cary 100 spectrophotometer (Varian).