Ca2+ activates actin-filament sliding on scallop myosin but inhibits that on Physarum myosin.
The actin-activated ATPase activity of Physarum myosin has been shown to be inhibited by microM levels of Ca2+, the mode of which is in contrast to the activating effect of Ca2+ on scallop myosin (Kohama, K. (1987) Adv. Biophys. 23, 149-182 for a review). To determine if Ca2+ regulates ATP-dependent sliding between actin and the myosins, fluorescent actin-filaments were allowed to move on the myosins fixed to a glass surface. The movement on Physarum and scallop myosins was inhibited and activated, respectively, by Ca2+. For this myosin-linked regulation to occur for Physarum myosin, myosin phosphorylation was shown to be a prerequisite.
Okagaki
T
T
Department of Pharmacology, Faculty of Medicine, University of Tokyo.
Higashi-Fujime
S
S
Kohama
K
K
D000199:Actins / Q000502:physiology*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000502:physiology*; D008974:Mollusca / Q000502:physiology; D009218:Myosins / Q000502:physiology*; D010766:Phosphorylation; D010804:Physarum / Q000502:physiology; D013045:Species Specificity
D000199:Actins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D009218:Myosins; D002118:Calcium