Adams R J, Pollard T D
Nature. 1986;322(6081):754-6. doi: 10.1038/322754a0.
Eukaryotic cells are dependent on their ability to translocate membraneous elements about the cytoplasm. In many cells long translocations of organelles are associated with microtubules. In other cases, such as the rapid cytoplasmic streaming in some algae, organelles appear to be propelled along actin filaments. It has been assumed, but not proven, that myosin produces these movements. We have tested vesicles from another eukaryotic cell for their ability to move on the exposed actin bundles of Nitella as an indiction that actin-based organelle movements may be a general property of cells. We found that organelles from Acanthamoeba castellanii can move along Nitella actin filaments. Here, we report two different experiments indicating that the single-headed non-polymerizable myosin isozyme myosin-I is responsible for this organelle motility. First, monoclonal antibodies to myosin-I inhibit movement, but antibodies that inhibit double-headed myosin-II do not. Second, approximately 20% of the myosin-I in homogenates co-migrates with motile vesicles during Percoll density-gradient ultracentrifugation. This is the first indication of a role for myosin-I within the cell and supports the suggestion of Albanesi et al. that myosin-I moves vesicles in this way.
真核细胞依赖于其在细胞质中转运膜性成分的能力。在许多细胞中，细胞器的长距离转运与微管有关。在其他情况下，如某些藻类中快速的细胞质环流，细胞器似乎是沿着肌动蛋白丝被推动的。人们已经假定，但尚未证实，肌球蛋白产生这些运动。我们测试了来自另一种真核细胞的囊泡在裸藻暴露的肌动蛋白束上移动的能力，以此作为基于肌动蛋白的细胞器运动可能是细胞普遍特性的一种指示。我们发现来自卡氏棘阿米巴的细胞器能够沿着裸藻肌动蛋白丝移动。在此，我们报告两个不同的实验，表明单头不可聚合的肌球蛋白同工酶肌球蛋白 -I 负责这种细胞器的运动性。首先，针对肌球蛋白 -I 的单克隆抗体抑制运动，但抑制双头肌球蛋白 -II 的抗体则不然。其次，在 Percoll 密度梯度超速离心过程中，匀浆中约 20%的肌球蛋白 -I 与运动囊泡共同迁移。这是肌球蛋白 -I 在细胞内发挥作用的首个迹象，并支持了阿尔巴内西等人提出的肌球蛋白 -I 以这种方式移动囊泡的观点。
