Polyamine Sharing between Tubulin Dimers Favours Microtubule Nucleation and Elongation via Facilitated Diffusion
Figure 3
High resolution AFM images of microtubules in the presence of spermidine in buffer M.
Scan area: 4×4 µm2. (A) 200 µM spermidine. (B) 800 µM spermidine. At moderate spermidine concentrations (<400 µM), long microtubules coexist with free tubulin dimers like in the absence of polyamines. Increasing polyamine concentration leads to the appearance of small tubulin oligomers or aggregates (green circles), microtubule bundles (arrow) and smaller microtubules. Interestingly oligomers or aggregates can also be adsorbed on MT surface (pink circles), as predicted for strong attractions (Regime III).