Structural basis of kinesin-1 autoinhibition and its control of microtubule-based motility
Kinesin-1, a heterotetramer of two kinesin heavy chains (KHC) and two kinesin light chains (KLC), drives microtubule-based transport of organelles and macromolecules, and its dysfunction is linked to ALS and hereditary spastic paraplegia. In the absence of cargo or activating factors, it adopts a compact autoinhibited conformation, but the molecule’s length and flexibility had prevented structural characterization of this state. We determined the first cryo-EM structure of the full-length autoinhibited kinesin-1 heterotetramer. The KLC cargo-binding TPR domains mediate fold-back of the KHC, and the resulting assembly restrains motor domain mobility while occluding cargo-binding surfaces on both the KHC tail and the KLC TPR domains. An asymmetric arrangement of the two KLC TPR domains is critical for stabilizing the folded KHC and constraining the motor domains.The structure suggests that MAP7 relieves autoinhibition by competing with the intramolecular contacts that maintain the folded state.