CYK4 relaxes the bias in the off-axis motion by MKLP1 kinesin-6

Abstract Centralspindlin, a complex of the MKLP1 kinesin-6 and CYK4 GAP subunits, plays key roles in metazoan cytokinesis. CYK4-binding to long neck region restricts configuration two motor domains centralspindlin. However, it is unclear how modulates interaction with microtubule. Here, we performed three-dimensional nanometry microbead coated multiple molecules on freely suspended We found that beads driven by dimeric exhibited persistently left-handed helical trajectories around microtubule axis, indicating torque generation. By contrast, centralspindlin, like monomeric MKLP1, showed similarly but less persistent movement occasional rightward movements. Analysis fluctuating indicated stochastically makes off-axis motions biased towards protofilament left. enables more flexible motion which would help avoid obstacles along crowded spindle microtubules.