Exploring the contribution of collective motions to the dynamics of forced-unfolding in tubulin.

Decomposition of the intrinsic dynamics of proteins into collective motions among distant regions of the protein structure provides a physically appealing approach that couples the dynamics of the system with its functional role. The cellular functions of microtubules (an essential component of the cytoskeleton in all eukaryotic cells) depend on their dynamic instability, which is altered by various factors among which applied forces are central. To shed light on the coupling between forces and the dynamic instability of microtubules, we focus on the investigation of the response of the microtubule subunits (tubulin) to applied forces. We address this point by adapting an approach designed to survey correlations for the equilibrium dynamics of proteins to the case of correlations for proteins forced-dynamics. The resulting collective motions in tubulin have a number of functional implications, such as the identification of long-range couplings with a role in blocking the dynamic instability of microtubules. A fundamental implication of our study for the life of a cell is that, to increase the likelihood of unraveling of large cytoskeletal filaments under physiological forces, molecular motors must use a combination of pulling and torsion rather than just pulling.