Caldesmon inhibits skeletal actomyosin subfragment-1 ATPase activity and the binding of myosin subfragment-1 to actin.

摘要: Smooth muscle contraction is controlled in part by the state of phosphorylation myosin. A recently discovered actin and calmodulin-binding protein, named caldesmon, may also be involved regulation smooth contraction. Caldesmon cross-links filaments inhibits actin-activated ATP hydrolysis myosin, particularly presence tropomyosin. We have studied effect caldesmon on rate skeletal myosin subfragment-1, a system which not important regulation. very effective inhibitor giving up to 95% inhibition. At low ionic strength (approximately 20 mM) this does require tropomyosin, whereas at high 120 tropomyosin enhances inhibitory activity concentrations. Cross-linking essential for inhibition occur since there little cross-linking as determined speed sedimentation assay. Under all conditions examined, decrease accompanied binding subfragment-1 actin. Furthermore, weakens equilibrium pyrophosphate. conclude that has general weakening responsible hydrolysis.