title: Troponin and its components from ascidian smooth muscle.
abstract: Troponin was isolated from the thin filaments of ascidian smooth muscle and separated into three components by ion-exchange chromatography, the molecular weights of which were 33,000, 24,000, and 18,000, respectively. The three components were designated as troponin t (TN-T), troponin I (TN-I), and troponin C (TN-C) in order of molecular weight, since each component had properties similar to those of the respective components of vertebrate skeletal-muscle troponin. The ascidian troponin or the mixture of the three components conferred Ca2+-sensitivity on reconstituted rabbit actomyosin in the presence of tropomyosin. One of the characteristics of the ascidian troponin was Ca2+-dependent activation of actin-myosin interaction in collaboration with tropomyosin, whereas its inhibitory action on the actomyosin ATPase in the absence of Ca2+ was less remarkable. From this, it is concluded that in the ascidian smooth muscle actin-myosin interaction is regulated by an actin-linked troponin-tropomyosin system, but the ascidian troponin acts as a Ca2+-dependent activator of an actomyosin system.
mesh_terms: D000205:Actomyosin / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D005779:Immunodiffusion; D008970:Molecular Weight; D009124:Muscle Proteins / Q000302:isolation & purification*; D009130:Muscle, Smooth / Q000032:analysis*; D011817:Rabbits; D014335:Tropomyosin / Q000378:metabolism; D014336:Troponin / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology; D014561:Urochordata / Q000032:analysis*
chemical_list: D009124:Muscle Proteins; D014335:Tropomyosin; D014336:Troponin; D000205:Actomyosin; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium