Polyamine Sharing between Tubulin Dimers Favours Microtubule Nucleation and Elongation via Facilitated Diffusion
Figure 6
Attraction of tubulin dimers onto microtubule mediated by spermidine.
0.3 µM of Cy3-labeled tubulin was allowed to interact with 4 µM of non fluorescent taxol-stabilized microtubules at various concentrations of spermidine (buffer M without GTP and without free taxol). The fluorescence intensity of both pellets and supernatants were then measured after centrifugation at 20,000×g for 10 min. The results show that Cy3-tubulin co-precipitated with microtubules at spermidine concentrations higher than 10 µM (under the conditions tested, we measured that no fluorescent tubulins sedimented in the absence of microtubules).