Abstract
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.