title: Differences between smooth and skeletal muscle myosins in their interactions with F-actin.
abstract: Myosin and F-actin were prepared from bovine carotid arterial smooth muscle and the properties of the binding of myosin to F-actin were compared with those of the binding of skeletal muscle myosin to F-actin. The following differences were observed between skeletal and smooth muscle myosins. 1. The rate of ATP-induced dissociation of arterial actomyosin was equal to that of hybrid actomyosin reconstituted from arterial myosin and skeletal muscle F-actin, but was much lower than those of skeletal muscle actomyosin and of hybrid actomyosin reconstituted from skeletal muscle myosin and arterial F-actin. 2. The amount of ATP necessary for complete dissociation of arterial actomyosin was 2 mol/mol of myosin, although it is well known that skeletal muscle actomyosin is dissociated completely by the addition of 1 mol ATP per mol of myosin. 3. Arterial actomyosin and hybrid actomyosin reconstituted from arterial myosin and skeletal muscle F-actin did not dissociate upon addition of 0.1 mM PPi, while skeletal muscle actomyosin dissociated completely. 4. In the absence of Mg2+, neither dissociation by ATP nor ATPase [EC 3.6.1.3] activity was observed with arterial actomyosin and hybrid actomyosin reconstituted from arterial myosin and skeletal muscle F-actin. On the other hand, skeletal muscle actomyosin dissociated almost completely upon addition of ATP and showed a considerably high ATPase activity. These observations reveal marked differences between myosins from skeletal and smooth muscles in their binding properties to F-actin.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000205:Actomyosin / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D002339:Carotid Arteries / Q000378:metabolism; D002417:Cattle; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009130:Muscle, Smooth / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D011817:Rabbits
chemical_list: D000199:Actins; D000205:Actomyosin; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; C026049:EDTA-ATPase; D009218:Myosins; D008274:Magnesium