Doublecortin engages the microtubule lattice through a cooperative binding mode involving its C-terminal domain

Doublecortin (DCX) is a microtubule (MT) associated protein that regulates MT structure and function during neuronal development and mutations in DCX lead to a spectrum of neurological disorders. The structural properties of MT-bound DCX remain poorly resolved. Here, we describe the molecular architecture of the DCX-MT complex through an integrative modeling approach that combines data from X-ray crystallography, cryo-EM and a high-fidelity chemical crosslinking method. We demonstrate that DCX interacts with MTs through its N-terminal domain and induces a lattice-dependent self-association involving both the C-terminal structured domain and the C-tails, in a conformation that favors an open, domain-swapped state. The networked state can accommodate multiple different attachment points on the MT lattice, all of which orient the C-tails away from the lattice. As numerous disease mutations cluster in the C-terminus, and regulatory phosphorylations cluster in the C-tail, our study shows that lattice-driven self-assembly is an important property of DCX.