Fig. 2: Experimental setup of the tubulin pulling assay using an optical trap.

Tubulin labeled with an oligo-DNA handle using the SSL method was linked to a long DNA linker through hybridization. Tubulin conjugated to the DNA-linker was polymerized with biotinylated tubulin and affixed to the surface of neutravidin-coated coverslips. The anti-digoxigenin antibody-coated microspheres were then bound to the DNA-linker labeled with digoxigenin. The mechanical force was exerted onto the α-tubulin CTT by pulling the microsphere with the optical trap along the y-axis, which is perpendicular to the long axis of microtubule (x-axis).