Williamson R E
Eur J Cell Biol. 1979 Dec;20(2):177-83.
Perfused Chara cells capable of resuming ATP-dependent cytoplasmic streaming in low free Ca++ solutions have been examined by electron microscopy for myosin-like filaments. Filaments 44 nm in diameter and up to 3 micron in length have been found associated with the endoplasmic reticulum that along with mitochondria, microbodies and dictyosomes from the endoplasm becomes immobilised around the sub-cortical actin bundles when ATP is depleted. Such endoplasmic filaments have not been detected in association with mitochondria or microbodies and they have not been found in the stationary cortex. These filaments are extracted from the perfused cell by ATP unless motility-inhibiting levels of cytochalasin B are present. The filaments are not detectable in cells inactivated in solutions containing high (10(-4) M) Ca++ concentrations even when the Ca++ level is subsequently lowered. Consistent with their being required for motility, cytoplasmic streaming cannot be effeiciently reactivated by ATP in such filament-depleted cells. The possibility is discussed that the filaments contain myosin and that the endoplasmic reticulum with which they are associated has a major role in generating and transmitting the motive force for streaming.
能够在低游离钙离子溶液中恢复依赖ATP的细胞质流动的灌注轮藻细胞，已通过电子显微镜检查其中是否存在类肌球蛋白丝。已发现直径为44纳米、长度达3微米的丝与内质网相关联，当ATP耗尽时，内质网连同线粒体、微体和来自内质的高尔基体在亚皮质肌动蛋白束周围固定下来。尚未检测到这种内质丝与线粒体或微体相关联，并且在静止的皮层中也未发现它们。除非存在抑制运动的细胞松弛素B水平，否则这些丝会被ATP从灌注细胞中提取出来。即使随后降低钙离子水平，在含有高（10⁻⁴ M）钙离子浓度的溶液中失活的细胞中也检测不到这些丝。与它们是运动所必需的一致，在这种丝缺失的细胞中，细胞质流动不能被ATP有效地重新激活。文中讨论了这种丝含有肌球蛋白以及与之相关的内质网在产生和传递流动动力方面起主要作用的可能性。
