Structural Delineation of the Neck Linker of Kinesin-3 for Processive Movement

Processive kinesin motors contain a neck linker (NL) that mediates the chemo-mechanical coupling and controls the directionality and processivity. However, kinesin-3 NL remains poorly determined due to the lack of the structural information of the junction with the following neck coil (NC). Here, we determined the structure of the motor domain (MD)–NL–NCNT tandem of KIF13B that defines the junction between NL and NC and delineates kinesin-3 NL. Unexpectedly, the length of kinesin-3 NL is much shorter than the previously predicted one. In the MD–NL–NCNT structure, NL docks onto the MD with a conventional mode but the interaction between NL and the MD is relatively weak due to the shorter N-terminal cover strand of the MD. The optimal short NL and its weak interaction with the MD would generate the tight inter-head strain and facilitate the NL undocking, which may contribute to the fast and superprocessive motility of kinesin-3. [Display omitted] •Kinesin-3 NL controls the directionality and processivity but is poorly defined.•Structure of the KIF13B MD–NL–NCNT tandem was determined at 2.0-Å resolution.•Kinesin-3 NL is shorter than the predicted one and is even shorter than kinesin-1 NL.•Kinesin-3 NL interacts weakly with MD due to the shorter N-terminal cover strand.•Short NL and its weak interaction with MD account for kinesin-3 processive movement.