The effect of polyamines on tubulin assembly

The assembly of cold solubilized microtubules prepared from calf brain and the polymerization of tubulin purified from this material are facilitated by polyamines at physiological concentrations. The number of free amino groups in the polyamine determines the ability of the polyamines to promote microtubule formation. Spermine with four amino groups was the most effective polyamine tested. Spermidine and N'-acetylspermine with 3 amino groups were less effective than spermine but more effective than N8-acetylspermidine and putrescine which contain two free amino groups. Microtubule formation may therefore be controlled by alterations in the nature and amounts of polyamines present.