Movie S1.

Example movie of growth assay with 1.0 μM Tub2-KCK and 0.5 nM of 20-nm gold nanoparticles present (2 frames per second). Gold-Tub2-KCK can occasionally be seen incorporating into growing microtubule tips. Microtubules (unlabeled) continue to grow after gold-Tub2-KCK incorporation. Notably, new gold only appears at growing microtubule tips. Scale bar 2.5 μm.