National Center for
2XRP: Human Doublecortin N-DC Repeat (1MJD) and Mammalian Tubulin (1JFF and 3HKE) Docked into the 8-Angstrom Cryo-EM Map of Doublecortin- Stabilised Microtubules
J. Cell Biol. (2010) 191 p.463-470
Microtubule-associated proteins (MAPs) are essential for regulating and organizing cellular microtubules (MTs). However, our mechanistic understanding of MAP function is limited by a lack of detailed structural information. Using cryo-electron microscopy and single particle algorithms, we solved the 8 A structure of doublecortin (DCX)-stabilized MTs. Because of DCX's unusual ability to specifically nucleate and stabilize 13-protofilament MTs, our reconstruction provides unprecedented insight into the structure of MTs with an in vivo architecture, and in the absence of a stabilizing drug. DCX specifically recognizes the corner of four tubulin dimers, a binding mode ideally suited to stabilizing both lateral and longitudinal lattice contacts. A striking consequence of this is that DCX does not bind the MT seam. DCX binding on the MT surface indirectly stabilizes conserved tubulin-tubulin lateral contacts in the MT lumen, operating independently of the nucleotide bound to tubulin. DCX's exquisite binding selectivity uncovers important insights into regulation of cellular MTs.