Murray J M
J Cell Sci. 1981 Jun;49:99-117. doi: 10.1242/jcs.49.1.99.
The euglenoid flagellates are able to change their shape rapidly in response to a variety of stimuli, or sometimes spontaneously. Two extremes of shape can be identified: the "relaxed" form is cylindrical; the contracted form is a somewhat distorted disc. These 2 forms can be interconverted by treatments that alter the Ca2+ concentration of the entire cell. The level of Ca2+ is believed to be normally controlled by a system of calcium-accumulating membranes, identified in Astasia longa by the technique of calcium oxalate precipitation. The system forms a set of parallel tubes of endoplasmic reticulum, one of which lies immediately below each of the ridges of the pellicle. The individual ridges, each with its associated reticulum, microtubules and other elements are suggested to be independent motor units. Local activation of a small number of these units by Ca2+ is made possible by the arrangement of Ca2+ -sequestering reticulum, producing the characteristic squirming euglenoid movement. Uniform activation or suppression of all units produces the 2 extremes of shape. The pellicle of A. longa with its associated microtubules has been purified and shown to contain a Ca2+ -binding site and ATPase activity.
裸藻鞭毛虫能够根据各种刺激迅速改变其形状，有时也会自发改变。可以识别出两种极端形状：“松弛”形式是圆柱形；收缩形式是有点扭曲的圆盘形。通过改变整个细胞的Ca2+浓度的处理，可以使这两种形式相互转换。据信Ca2+水平通常由钙积累膜系统控制，在长眼虫中通过草酸钙沉淀技术鉴定出该系统。该系统形成一组平行的内质网管，其中一根位于表膜的每条嵴的正下方。每个单独的嵴及其相关的内质网、微管和其他成分被认为是独立的运动单元。Ca2+隔离内质网的排列使得少数这些单元通过Ca2+进行局部激活成为可能，从而产生特征性的扭动裸藻运动。所有单元的均匀激活或抑制产生两种极端形状。长眼虫的表膜及其相关的微管已被纯化，并显示含有一个Ca2+结合位点和ATP酶活性。
