title: Modulation of smooth muscle actomyosin ATPase by thin filament associated proteins.
abstract: Caldesmon binds equally to both gizzard actin and actin containing stoichiometric amounts of bound tropomyosin. The binding of caldesmon to actin inhibits the actin-activation of the Mg-ATPase activity of phosphorylated myosin only when the actin contains bound tropomyosin. The reversal of this inhibition requires Ca2+-calmodulin; but it occurs without complete release of bound caldesmon. Although phosphorylation of the caldesmon occurs during the ATPase assay, a direct correlation between caldesmon phosphorylation and the release of the inhibited actomyosin ATPase is not consistently observed.
mesh_terms: D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000494:pharmacology*; D002645:Chickens; D007700:Kinetics; D009130:Muscle, Smooth / Q000201:enzymology*; D010766:Phosphorylation; D014335:Tropomyosin / Q000378:metabolism
chemical_list: D000199:Actins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D014335:Tropomyosin; D000205:Actomyosin; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium