Tseng Kuo-Fu, Wang Pan, Lee Yuh-Ru Julie, Bowen Joel, Gicking Allison M, Guo Lijun, Liu Bo, Qiu Weihong
Department of Physics, Oregon State University, Corvallis, OR, 97331, USA.
Institute of Photobiophysics, Henan University, Kaifeng, 475004, Henan, China.
Nat Commun. 2018 Mar 14;9(1):1067. doi: 10.1038/s41467-018-03480-w.
In animals and fungi, cytoplasmic dynein is a processive minus-end-directed motor that plays dominant roles in various intracellular processes. In contrast, land plants lack cytoplasmic dynein but contain many minus-end-directed kinesin-14s. No plant kinesin-14 is known to produce processive motility as a homodimer. OsKCH2 is a plant-specific kinesin-14 with an N-terminal actin-binding domain and a central motor domain flanked by two predicted coiled-coils (CC1 and CC2). Here, we show that OsKCH2 specifically decorates preprophase band microtubules in vivo and transports actin filaments along microtubules in vitro. Importantly, OsKCH2 exhibits processive minus-end-directed motility on single microtubules as individual homodimers. We find that CC1, but not CC2, forms the coiled-coil to enable OsKCH2 dimerization. Instead, our results reveal that removing CC2 renders OsKCH2 a nonprocessive motor. Collectively, these results show that land plants have evolved unconventional kinesin-14 homodimers with inherent minus-end-directed processivity that may function to compensate for the loss of cytoplasmic dynein.
在动物和真菌中，细胞质动力蛋白是一种进行性的负端定向马达蛋白，在各种细胞内过程中起主导作用。相比之下，陆生植物缺乏细胞质动力蛋白，但含有许多负端定向的驱动蛋白-14。目前已知没有植物驱动蛋白-14作为同二聚体产生进行性运动。OsKCH2是一种植物特有的驱动蛋白-14，具有一个N端肌动蛋白结合结构域和一个位于两个预测的卷曲螺旋（CC1和CC2）侧翼的中央马达结构域。在这里，我们表明OsKCH2在体内特异性地修饰前期带微管，并在体外沿着微管运输肌动蛋白丝。重要的是，OsKCH2作为单个同二聚体在单个微管上表现出进行性的负端定向运动。我们发现CC1而非CC2形成卷曲螺旋以实现OsKCH2二聚化。相反，我们的结果表明去除CC2会使OsKCH2成为非进行性马达蛋白。总的来说，这些结果表明陆生植物已经进化出具有内在负端定向进行性的非常规驱动蛋白-14同二聚体，其可能起到补偿细胞质动力蛋白缺失的作用。
