title: Calcium sensitivy of foot muscle myosin from clam (Meretrix lusoria).
abstract: 1. It was found that Mg-ATPase of clam foot myosin is strongly activated by calcium or strontium ions and is as sensitive to those divalent cations as the Mg-ATPase and superprecipitation of rabbit skeletal acto-clam foot myosin are. 2. It was also found that desensitization and resensitization of clam foot myosin result in the loss of superprecipitation activity with acto-desensitized myosin and in its recovery with acto-resensitized myosin, respectively. However, the ATP-ASE activity in the absence of calcium ions rises with acto-desensitized myosin and falls again with acto-resensitized myosin. 3. It is thus proposed that the primary role of the EDTA-light chain component in calcium regulation is to inhibit myosin-ATPase rather than to inhibit the actin-myosin interaction.
mesh_terms: D000199:Actins / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D049872:Bivalvia; D002118:Calcium / Q000494:pharmacology*; D004789:Enzyme Activation; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009132:Muscles / Q000201:enzymology*; D009218:Myosins / Q000378:metabolism*; D013324:Strontium / Q000494:pharmacology
chemical_list: D000199:Actins; D000255:Adenosine Triphosphate; D009218:Myosins; D008274:Magnesium; D002118:Calcium; D013324:Strontium