A. Isosurface top view of the whole 13-PF MT cylinder and a side view close-up on NN binding site at the vertex of 4 tubulin dimers, where NDC of NN decorates the MT lattice. α-tubulin, white; β-tubulin, grey; NDC, blue. The valley between PFs 1 and 13 represents MT seam, where NN does not bind. 