Biomolecular motor modulates mechanical property of microtubule.

The microtubule (MT) is the stiffest cytoskeletal filamentous protein that takes part in a wide range of cellular activities where its mechanical property plays a crucially significant role. How a single biological entity plays multiple roles in cell has been a mystery for long time. Over the recent years, it has been known that modulation of the mechanical property of MT by different cellular agents is the key to performing manifold in vivo activities by MT. Studying the mechanical property of MT thus has been a prerequisite in understanding how MT plays such diversified in vivo roles. However, the anisotropic structure of MT has been an impediment in obtaining a precise description of the mechanical property of MT along its longitudinal and lateral directions that requires employment of distinct experimental approach and has not been demonstrated yet. In this work, we have developed an experimental system that enabled us to investigate the effect of tensile stress on MT. By using our newly developed system, (1) we have determined the Young's modulus of MT considering its deformation under applied tensile stress and (2) a new role of MT associated motor protein kinesin in modulating the mechanical property of MT was revealed for the first time. Decrease in Young's modulus of MT with the increase in interaction with kinesin suggests that kinesin has a softening effect on MT and thereby can modulate the rigidity of MT. This work will be an aid in understanding the modulation of mechanical property of MTs by MT associated proteins and might also help obtain a clear insight of the endurance and mechanical instability of MTs under applied stress.