Chara myosin is a plant myosin involved in cytoplasmic streaming of
Characean cells and the fastest of all myosins observed so far with
in vitro motility assay. Movement of F-actin on
Chara myosin was completely inhibited by muscle tropomyosin. In concert with this, the actin activated
Chara myosin ATPase was also completely inhibited by tropomyosin. The movement of the thin filament of F-actin with native tropomyosin, the complex of tropomyosin and troponin, was inhibited on
Chara myosin and the actin activated ATPase of
Chara myosin was also inhibited by native tropomyosin. With careful observations,
Chara myosin occasionally moved actin filaments in the presence of native tropomyosin and Ca
2+. This indicates that the effect of tropomyosin of the thin filament in the“ON”state is not exactly the same as that of tropomyosin alone on F-actin.
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