Effect of calponin on actin-activated myosin ATPase activity.
Calponin inhibited the actin-activated myosin MgATPase activity in a dose-dependent manner without affecting the phosphorylation level of myosin light chain. This inhibition was Ca2(+)-independent. The decrease in enzymatic activity of myosin was correlated with binding of calponin to actin-tropomyosin filaments. Caldesmon showed a further inhibition of the calponin-induced inhibition of MgATPase activity of the thiophosphorylated myosin. Calponin-induced inhibition of the myosin MgATPase activity was reversed by the addition of calmodulin only in the presence of Ca2+. These results suggest that calponin acts as an inhibitory component of smooth muscle thin filaments.
Abe
M
M
Second Department of Internal Medicine, Ehime University School of Medicine.
Takahashi
K
K
Hiwada
K
K
D000199:Actins / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology; D002148:Calmodulin-Binding Proteins / Q000494:pharmacology; D002645:Chickens; D004789:Enzyme Activation / Q000187:drug effects; D005895:Gizzard, Avian / Q000187:drug effects / Q000201:enzymology; D008840:Microfilament Proteins; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology*; D009218:Myosins / Q000378:metabolism*; D000096985:Calponins
D000199:Actins; D002118:Calcium; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D008840:Microfilament Proteins; D009218:Myosins; D000096985:Calponins