Fig. 1.

Splaying relaxation of the MT plus-end tip. (A) Biochemical basis of force generation by polymerizing and depolymerizing MTs (adapted from refs. 9, 11, 14, 26). (Top) An MT growing against an intracellular obstacle, e.g., lipid membranes, organelles, or other protein complexes. Stochastic fluctuations allow for incorporation of tubulin dimers into the lattice, leading to a displacement or deformation of the obstacle (assuming the minus-end is fixed). (Bottom) Schematic showing the attachment of the MT tip to the Ndc80-Dam1 kinetochore complex that is thought to slide toward the minus-end using the mechanical force transmitted from peeling PFs during MT depolymerization (assuming the minus-end is fixed). (B) Side and top views of the starting MT tip structure. Atomistic structures are shown in surface representation. The lowest row of tubulin monomers at the minus-end were restrained during the simulations. The position of the seam is indicated with a dashed line. (C) Top view of the GTP- (orange) and GDP-MT (blue) tip structures after $1\hspace{0.17em}\text{μ}$s of simulation. The seams are indicated with dashed lines. (D) Traces of the PFs aligned with respect to the minus-end monomer and projected onto the radial (Left) and axial (Right) planes. Random colors were assigned for clarity.