15 angstrom resolution model of the monomeric kinesin motor, KIF1A

A two-headed structure has been widely believed to be essential for the kin esin molecular motor to move processively on the track, microtubules. Howev er, we have recently demonstrated that a monomeric motor domain construct o f KIF1A (C351), a kinesin superfamily protein, moves processively, taking a bout 700 steps before being detached from microtubules. To elucidate the me chanism of its single-headed processivity, we examined the C351-MT interact ion by mutant analysis and high-resolution cryo-EM. Mutant analysis indicat ed the importance of a highly positively charged loop, the "K loop," for su ch processivity A15 Angstrom resolution structure unambiguously docked with the available atomic models revealed "K loop" as an extra microtubule-bind ing domain specific to KIF1A, and bound to the C terminus of tubulin. The s ite-specific crosslinking further confirmed this model.