Figure 4.

Models for the Ndc80 force coupler during polymerization in wild type and consequences of Dam1 mutants in which the kinetochore dislocates from the microtubule plus-end [58]. A: During polymerization, force from centromere stretch pulls the Ndc80 force coupler along kMTs with the microtubule binding domains of Dam1 and Ndc80 under tension. During depolymerization, forces from peeling protofilaments push the Dam1 and Ndc80 complexes along kMTs towards the pole to stretch the centromere; the MTBDs of both Dam1 and Ndc80 are under compression (not shown). C: Mutations in Dam1 that increase friction between Dam1 and the microtubule lattice may prevent kinetochores from keeping up with the ends of polymerizing microtubules, leading to dislocation of the kinetochore from the MT plus-end [70]. Ndc80 resistive tension (green arrow in C) from centromere stretch is reduced in this state with increased Dam1 friction (blue arrow in C). B and D: Snapshots of movies derived from 600 s duration simulations presented in [58], showing kinetics for all 16 sister kinetochore pairs and their centromere stretch. See Supporting Information to view the movies. B: WT, D: dam1 mutant.