title: Removal of troponin C and desensitization of myosin B from ascidian smooth muscle by treatment with ethylene diamine tetraacetate.
abstract: On treatment with 10 mM EDTA at 30 degrees C, protein of 18,000 daltons was released from myofibrils, thin filaments and myosin B prepared from the smooth muscle of an ascidian, Halocynthia roretzi. This protein was purified from the EDTA extract of myofibrils by differential centrifugation, freeze-drying and gel-filtration. Based on its molecular weight, electrophoretic mobilities in the presence and absence of Ca2+ and other properties, it was identified as troponin C. By EDTA treatment, ascidian myosin B lost the Ca2+-sensitivity of Mg2+-ATPase, and EDTA-treated myosin B recovered the sensitivity by mixing with the EDTA extract of myosin B in the presence of Mg2+. Gel-electrophoretic patterns indicated that desensitization and resensitization of ascidian myosin B were accompanied by the removal and binding of troponin C. These results indicate that ascidian smooth muscle is regulated by a troponin-tropomyosin system, and desensitization induced by EDTA treatment is due to the removal of troponin C but not the release of the light chains of the myosin molecule. Based on these findings, we have established a simple method for the purification of troponin C from ascidian smooth muscle.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D004492:Edetic Acid; D004586:Electrophoresis / Q000379:methods; D009130:Muscle, Smooth / Q000032:analysis; D009218:Myosins / Q000302:isolation & purification*; D012967:Sodium Dodecyl Sulfate; D014336:Troponin / Q000302:isolation & purification*; D019209:Troponin C; D014508:Urea; D014561:Urochordata / Q000032:analysis*
chemical_list: D014336:Troponin; D019209:Troponin C; D012967:Sodium Dodecyl Sulfate; D014508:Urea; D004492:Edetic Acid; D000251:Adenosine Triphosphatases; D009218:Myosins