Smooth muscle calponin. Inhibition of actomyosin MgATPase and regulation by phosphorylation.

摘要: Calponin isolated from chicken gizzard smooth muscle inhibits the actin-activated MgATPase activity of myosin in a reconstituted system composed contractile and regulatory proteins. ATPase inhibition is not due to phosphorylation since, at calponin concentrations sufficient cause maximal inhibition, was unaffected. Furthermore, inhibited fully phosphorylated or thiophosphorylated myosin. Although Ca2(+)-binding protein, did require Ca2+. although also binds tropomyosin, dependent on presence tropomyosin. vitro by protein kinase C Ca2+/calmodulin-dependent II, but cAMP- cGMP-dependent kinases, light chain kinase. Phosphorylation either resulted loss its ability inhibit actomyosin ATPase. The retained calmodulin tropomyosin binding capabilities, actin greatly reduced. calponin-actin interaction, therefore, appears be responsible for These observations suggest that may involved regulating actin-myosin interaction and, state muscle. function turn regulated Ca2(+)-dependent phosphorylation.