Tight bending of the Ndc80 complex provides intrinsic regulation of its binding to microtubules.

Regulation of the outer kinetochore complex Ndc80 is essential to ensure correct kinetochore-microtubule attachments during mitosis. Here, we present a novel mechanism of regulation that is intrinsic to its structure; tight bending of the Ndc80 complex inhibits its microtubule binding. Using single molecule Förster resonance energy transfer (FRET), we show that the Ndc80 complex can fluctuate between straight and bent forms, and that binding of the complex to microtubules selects for straightened forms.