Department of Molecular Biology, Faculty of Science, Nagoya University, Nagoya, Japan.
Proc Jpn Acad Ser B Phys Biol Sci. 2012;88(5):201-11. doi: 10.2183/pjab.88.201.
Chara myosin is plant myosin responsible for cytoplasmic streaming and moves actin filaments at 60 µm/s, which is the fastest of all myosins examined. The neck of the myosin molecule has usually mechanical and regulatory roles. The neck of Chara myosin is supposed to bind six light chains, but, at present, we have no knowledge about them. We found Ca⁺⁺-calmodulin activated Chara myosin motility and its actin-activated ATPase, and actually bound with the Chara myosin heavy chain, indicating calmodulin might be one of candidates for Chara myosin light chains. Antibody against essential light chain from Physarum myosin, and antibodies against Chara calmodulin and chicken myosin light chain from lens membranes reacted with 20 kDa and 18 kDa polypeptides of Chara myosin preparation, respectively. Correspondingly, column purified Chara myosin had light chains of 20 kDa, and 18 kDa with the molar ratio of 0.7 and 2.5 to the heavy chain, respectively.
肌球蛋白是植物肌球蛋白，负责细胞质流动，以 60 µm/s 的速度移动肌动蛋白丝，这是所有研究过的肌球蛋白中最快的。肌球蛋白分子的颈部通常具有机械和调节作用。查拉肌球蛋白的颈部应该结合六个轻链，但目前我们对它们一无所知。我们发现 Ca⁺⁺-钙调蛋白激活了查拉肌球蛋白的运动及其肌动蛋白激活的 ATP 酶，并与查拉肌球蛋白重链结合，表明钙调蛋白可能是查拉肌球蛋白轻链的候选者之一。来自粘菌肌球蛋白的必需轻链抗体，以及来自晶状体膜的查拉钙调蛋白和鸡肌球蛋白轻链的抗体，分别与查拉肌球蛋白制剂的 20 kDa 和 18 kDa 多肽反应。相应地，柱纯化的查拉肌球蛋白具有 20 kDa 和 18 kDa 的轻链，与重链的摩尔比分别为 0.7 和 2.5。
