High-Resolution structures of microtubule-bound KIF1A and its pathogenic variant P305L

Mutations in the microtubule-associated motor protein KIF1A lead to severe neurological conditions known as KIF1A-associated neurological disorders (KAND). Despite insights into its molecular mechanism, high-resolution structures of KIF1A-microtubule complexes remain undefined. Here, we present 2.7-3.4 [A] resolution structures of dimeric microtubule-bound KIF1A, including the pathogenic P305L mutant, across various nucleotide states. Our structures reveal that KIF1A binds microtubules in one- and two-heads-bound configurations, with both heads exhibiting distinct conformations with tight inter-head connection. Notably, KIF1As class-specific loop 12 (K-loop) forms electrostatic interactions with the C-terminal tails of both - and {beta}-tubulin. The P305L mutation does not disrupt these interactions but alters loop-12s conformation, impairing strong microtubule-binding. Structure-function analysis reveals the K-loop and head-head coordination as major determinants of KIF1As superprocessive motility. Our findings advance the understanding of KIF1As molecular mechanism and provide a basis for developing structure-guided therapeutics against KAND.