Effects of C-termini distribution on ion transport along microtubules

Recent experiments demonstrated that microtubules in solution serve as directional pathways for ionic conduction. Biochemical assays have revealed the existence of numerous isoforms of the building block of microtubules, the protein called tubulin. Each isoform differs structurally, especially in the composition of their C-terminal tails. We developed a computational model for ionic conduction along a microtubular structure. The model allows for ionic hopping and trapping by the oppositely charged C-termini tails. Our simulations include various scenarios of isoform distribution within a given microtubule. We show that a critical number of ions is required for the onset of conduction and that it obeys scaling laws with respect to the length and isoform composition. We also found the formation of complex conduction pathways that depend on the distribution of tubulin isoforms.