Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, Japan.
Komaba Institute for Science, The University of Tokyo, Meguro-ku, Tokyo, Japan.
Commun Biol. 2021 Feb 10;4(1):180. doi: 10.1038/s42003-021-01704-2.
Centralspindlin, a complex of the MKLP1 kinesin-6 and CYK4 GAP subunits, plays key roles in metazoan cytokinesis. CYK4-binding to the long neck region of MKLP1 restricts the configuration of the two MKLP1 motor domains in the centralspindlin. However, it is unclear how the CYK4-binding modulates the interaction of MKLP1 with a microtubule. Here, we performed three-dimensional nanometry of a microbead coated with multiple MKLP1 molecules on a freely suspended microtubule. We found that beads driven by dimeric MKLP1 exhibited persistently left-handed helical trajectories around the microtubule axis, indicating torque generation. By contrast, centralspindlin, like monomeric MKLP1, showed similarly left-handed but less persistent helical movement with occasional rightward movements. Analysis of the fluctuating helical movement indicated that the MKLP1 stochastically makes off-axis motions biased towards the protofilament on the left. CYK4-binding to the neck domains in MKLP1 enables more flexible off-axis motion of centralspindlin, which would help to avoid obstacles along crowded spindle microtubules.
中心纺锤体是 MKLP1 驱动蛋白-6 和 CYK4 GAP 亚基的复合物，在动物胞质分裂中发挥关键作用。CYK4 与 MKLP1 的长颈部结合限制了中心纺锤体中两个 MKLP1 运动结构域的构象。然而，CYK4 结合如何调节 MKLP1 与微管的相互作用尚不清楚。在这里，我们对涂有多个人 MKLP1 分子的微珠在自由悬挂的微管上进行了三维纳米测量。我们发现，由二聚体 MKLP1 驱动的微珠在微管轴周围表现出持久的左手螺旋轨迹，表明产生了扭矩。相比之下，中心纺锤体与单体 MKLP1 一样，表现出类似的但不太持久的左手螺旋运动，偶尔会出现向右运动。对波动的螺旋运动的分析表明，MKLP1 会随机做出偏离轴的运动，偏向左侧的原纤维。CYK4 与 MKLP1 颈部结构域的结合使中心纺锤体的离轴运动更加灵活，这有助于避免在拥挤的纺锤体微管中遇到障碍物。
