title: An activating factor (tropomyosin) for the superprecipitation of actomyosin prepared from scallop adductor muscles.
abstract: An activating factor for the superprecipitation of actomyosin reconstructed from scallop smooth muscle myosin and rabbit skeletal muscle F-actin was purified from thin filaments of scallop smooth and striated muscles. Two components were obtained from the smooth muscle and one from the striated muscle. All three components similarly affected the actomyosin ATPase activity. According to the results of analysis involving double reciprocal plotting of the ATPase activity versus F-actin concentration, the activating factor for superprecipitation decreased the apparent dissociation constants of actomyosin about 30 to 110 times. The activation of the superprecipitation by the factor, therefore, may be due to the enhancement of the affinity between F-actin and myosin in the presence of ATP. The activating factor was identified as tropomyosin based on it mobility on polyacrylamide gel electrophoresis and on the recovery of the Ca2+-sensitivity of purified rabbit skeletal actomyosin in the presence of troponin.
mesh_terms: D000199:Actins / Q000302:isolation & purification; D000205:Actomyosin / Q000302:isolation & purification*; D000251:Adenosine Triphosphatases / Q000302:isolation & purification; D000818:Animals; D011232:Chemical Precipitation; D004591:Electrophoresis, Polyacrylamide Gel; D008974:Mollusca / Q000032:analysis; D009132:Muscles / Q000032:analysis*; D011817:Rabbits; D014335:Tropomyosin / Q000302:isolation & purification*
chemical_list: D000199:Actins; D014335:Tropomyosin; D000205:Actomyosin; D000251:Adenosine Triphosphatases