In vitro formation of different tubulin polymers from purified tubulin of Ehrlich ascites tumor cells

Preparations of cycled tubulin from Ehrlich ascites tumor cells contain several accessory proteins; once or twice cycled microtubule preparations are usually composed of fibers 10 nm in diameter, but lack vimentin. Highly purified tubulin consists of alpha- and beta-tubulin and a minor component which was identified by peptide mapping as a second beta-chain. This pure tubulin is able to form in vitro at low concentrations (1 mg protein/ml) fibers of about 10 nm width, and at higher concentrations (3.5 mg protein/ml) normal microtubules.