Structure challenges in the multivalency of Tau-microtubule interactions

Structural studies aiming to visualize the interaction of Tau with microtubules (MTs) face several challenges, the main concerning the fact that Tau has multiple MT-interacting regions. In particular, the four (or three) pseudo-repeats of Tau bind to identical elements along the MT lattice but do it through non-identical residues. In addition, any given Tau molecule can use all its repeats or just one for its engagement with MTs. Finally, the binding of one Tau is not necessarily in register with respect to the next one. The mismatch in the MT and Tau repeats, therefore, challenges conventional modes of image analysis when visualizing these samples using cryo-electron microscopy. This commentary is dedicated to those challenges and ways to circumvent them while aiming for an atomic description of the Tau-tubulin interaction.