Kinesin heads fused to hinge-free myosin tails drive efficient motility.

The rat kinesin motor domain was fused at residues 433, 411, 376 or 367, respectively, to the C-terminal 1185, 1187, 1197 or 1185 residues of the brush border myosin tail. In motility assays, K433myt and K411myt, which preserve the head-proximal kinesin hinge, and K367myt, which deletes it, drove rapid microtubule sliding ( approximately 0.6 microms(-1)) that was optimal when the head-pairs were spaced apart by adding 1:1 headless myosin tails. K376myt, which partially deletes the head-proximal hinge, showed poor motility in sliding assays but wild type processivity, velocity and stall force in single molecule optical trapping. Accordingly, the head-proximal kinesin hinge is functionally dispensable.