Polyamine Sharing between Tubulin Dimers Favours Microtubule Nucleation and Elongation via Facilitated Diffusion
Figure 1
Schematic representation of the mechanism of facilitated diffusion.
(A) Attraction between two tubulin heterodimers mediated by polyamines. The attraction is mediated by the two C-terminal tails of one tubulin dimer, which, for entropic reasons (separation distance between the two C-termini tails on a tubulin dimer), are likely to share polyamines with two C-terminal tails of another tubulin dimer. (B) In the absence of an attraction force, many collisions between tubulin and nucleus do not result in association, whereas, in the presence of an attraction force, both facilitated diffusion via sliding and an increase of the interaction lifetime favour association to the growing nucleus. (C) In the presence of an attraction force, sliding of tubulin along the cylindrical surface of MT favours tubulin association to the MT ends.