BPS2026 – Structural basis of tubulin post translational modification recognition by EML proteins

Post-translational modifications (PTMs) of microtubule (MT) C-terminal tails modulate MT functions. A family of highly conserved MT binding proteins, the Echinoderm microtubule-associated protein-like (EML) family, regulates neuronal outgrowth and mitosis and are readers of MT PTMs. However, resolving the structural basis by which PTM reader proteins recognize PTMs has been challenging due to the intrinsic flexibility of the MT C-terminal tails. Using cryo-electron microscopy and single-molecule imaging, we uncovered the mechanism by which EML proteins recognize PTMs on the tubulin tail. Remarkably, our structures reveal the entire alpha-tubulin tail in a fully ordered conformation, enclosed within a beta-propeller domain of the EML protein. High-resolution structural analysis shows that this interaction is mediated by a unique tyrosine recognition motif, coupled with simultaneous binding across multiple tubulin dimers along the MT lattice. Furthermore, our structures of EML proteins from different species demonstrate that this motif is evolutionarily conserved and essential for their robust MT binding. Through single molecule imaging, we found that EML proteins preferentially associate with the GTP-like MT lattice and promote MT catastrophe events, in contrast to the stabilizing role typically attributed to many MT binding proteins. Together, our findings define a novel tubulin tyrosine recognition motif that is conserved within EML proteins, revealing the structural mechanism of how they bind to MTs and affect their dynamics.