Nakamura A, Kohama K
Department of Pharmacology, Gunma University School of Medicine, Japan.
Int Rev Cytol. 1999;191:53-98. doi: 10.1016/s0074-7696(08)60157-6.
Plasmodia of Physarum polycephalum show vigorous cytoplasmic streaming, the motive force of which is supported by the actin-myosin interaction. Calcium is not required for the interaction but inhibits it. This calcium inhibition, a regulatory mode first discovered in Physarum, is the overwhelming mode of regulation of cytoplasmic streaming of plant cells and lower eukaryotes, and it is diametrically opposite to calcium activation of the interaction found in muscle and nonmuscle cells of the animal kingdom. Myosin, myosin II in myosin superfamily, is the most important protein for Ca2+ action. Its essential light chain, called calcium-binding light chain, is the sole protein that binds Ca2+. Although phosphorylation and dephosphorylation of myosin modify its properties, regulation of physiological significance is shown to be Ca-binding to myosin. The actin-binding protein of Physarum amplifies calcium inhibition when Ca2+ binds to calmodulin and other calcium-binding proteins. This review also includes characterization of this and other calcium-binding proteins of Physarum.
多头绒泡菌的疟原虫表现出强烈的细胞质流动，其动力由肌动蛋白-肌球蛋白相互作用提供支持。钙对于这种相互作用不是必需的，但会抑制它。这种钙抑制作用是在绒泡菌中首次发现的一种调节模式，是植物细胞和低等真核生物细胞质流动的主要调节模式，并且与动物界肌肉和非肌肉细胞中发现的该相互作用的钙激活作用截然相反。肌球蛋白，即肌球蛋白超家族中的肌球蛋白II，是钙作用的最重要蛋白质。其必需轻链，称为钙结合轻链，是唯一结合钙的蛋白质。尽管肌球蛋白的磷酸化和去磷酸化会改变其特性，但生理意义上的调节显示为钙与肌球蛋白的结合。当钙离子与钙调蛋白和其他钙结合蛋白结合时，绒泡菌的肌动蛋白结合蛋白会放大钙抑制作用。本综述还包括对绒泡菌的这种及其他钙结合蛋白的特性描述。
