Figure 2.

Visualization of Tau and kinesin bound to microtubules. The diagram shows a Tau molecule and a kinesin motor domain bound to a microtubule protofilament (row of αβ-tubulin heterodimers). All molecules are in the same size range (∼350–450 residues), but tubulin and kinesin are compactly folded. Tau is not and therefore occupies a much larger volume, loosely filled with polypeptide chain and highly mobile. Structures modeled after Nogales et al. (1999) (tubulin), Sack et al. (1997) (kinesin), and Hoenger et al. (1998) (docking of kinesin on microtubule). Tau is shown as a random coil; its microtubule-bound conformation is not known. (Figure composed by A. Marx.)