Ligand Binding Swaps between Soft Internal Modes of α,β-Tubulin and Alters Its Accessible Conformational Space Sarmistha Majumdar Shubhra Ghosh Dastidar 10.1021/acs.jpcb.6b11322.s001 https://acs.figshare.com/articles/journal_contribution/Ligand_Binding_Swaps_between_Soft_Internal_Modes_of_-Tubulin_and_Alters_Its_Accessible_Conformational_Space/4487978 The dynamic instability of the microtubule originates from the conformational switching of its building block, that is, the α, β-tubulin dimer. Ligands occupying the interface of the α–β dimer bias the switch toward the disintegration of the microtubule, which in turn controls the cell division. A little loop of tubulin is structurally encoded as a biophysical “gear” that works by changing its structural packing. The consequence of such change propagates to the quaternary level to alter the global dynamics and is reflected as a swapping between the relative contributions of dominating internal modes. Simulation shows that there is an appreciable separation between the conformational space accessed by the liganded and unliganded systems; the clusters of conformations differ in their intrinsic tendencies to “bend” and “twist”. The correlation between the altered breathing modes and conformational space rationally hypothesizes a mechanism of straight−bent interconversion of the system. In this mechanism, a ligand is understood to bias the state of the “gear” that detours the conformational equilibrium away from its native preference. Thus, a fundamental biophysical insight into the mechanism of the conformational switching of tubulin is presented as a multiscale process that also shows promise to yield newer concept of ligand design. 2016-12-02 00:00:00 microtubule ligand design Accessible Conformational Space dimer quaternary level cell division Soft Internal Modes tubulin bias building block mechanism Ligand Binding Swaps change propagates multiscale process unliganded systems breathing modes