Template-free 13-protofilament microtubule-MAP assembly visualized at 8 A resolution.
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 Å 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.
Fourniol
Franck J
FJ
Institute of Structural and Molecular Biology, Birkbeck College, London, England, UK.
Sindelar
Charles V
CV
Amigues
Béatrice
B
Clare
Daniel K
DK
Thomas
Geraint
G
Perderiset
Mylène
M
Francis
Fiona
F
Houdusse
Anne
A
Moores
Carolyn A
CA
D001665:Binding Sites; D020285:Cryoelectron Microscopy; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism* / Q000648:ultrastructure*; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure*; D009479:Neuropeptides / Q000378:metabolism*
C000714328:DCX protein, human; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides