Theory of strength and stability of kinetochore-microtubule attachments: collective effects of dynamic load-sharing

Application of pulling force, under force-clamp conditions, to kinetochore-microtubule attachments in-vitro revealed a catch-bond-like behavior. In an earlier paper (Sharma et al. Phys. Biol. (2014) the physical origin of this apparently counter-intuitive phenomenon was traced to the nature of the force-dependence of the (de-)polymerization kinetics of the microtubules. In this brief communication that work is extended to situations where the external forced is ramped up till the attachment gets ruptured. In spite of the fundamental differences in the underlying mechanisms, the trend of variation of the rupture force distribution observed in our model kinetochore-microtubule attachment with the increasing loading rate is qualitatively similar to that displayed by the catch bonds formed in some other ligand-receptor systems. Our theoretical predictions can be tested experimentally by a straightforward modification of the protocol for controlling the force in the optical trap set up that was used in the original experiments under force-clamp conditions.